Hello, distance detective! In this chapter, you will choose useful units for very small lengths, room-sized lengths, and long journeys. A number becomes meaningful only when its unit is clear. Saying “450” is incomplete; saying “450 m” or “450 cm” tells the listener what kind of length you mean.
Caregiver: Keep measurement practice safe and local. Children can measure paper strips, books, steps inside a room, or a marked path with adult help. They should not walk away from home or school to measure distances alone.
This original guide follows Chapter 5, Far and Near, from NCERT’s Maths Mela for Class 5. The explanations, examples, activity, diagram, and practice questions are newly written for PrincipalSaab and do not copy textbook exercises, tables, or artwork.
Words to Know
millimetre (mm)
a very small length unit
thickness of a small object
centimetre (cm)
10 millimetres
length of a pencil piece
metre (m)
100 centimetres
height of a door
kilometre (km)
1000 metres
distance between places
inch (in)
a small customary length unit
short craft length
foot (ft)
12 inches
height of a small table
estimate
a sensible near value
a desk is about 1 m long
convert
write the same measure in another unit
200 cm = 2 m
remainder
the part left after making full groups
935 cm = 9 m and 35 cm
Measure five safe items or distances near your desk: a pencil, a notebook side, your table length, your room doorway, and ten careful steps in a straight line. Record each in the unit that makes it easiest to read. Ask an adult before measuring any shared or outdoor space. (15-20 min)
Your Learning Plan
- Decide whether the length is tiny, hand-sized, room-sized, or journey-sized.
- Use 10 mm = 1 cm, 100 cm = 1 m, and 1000 m = 1 km.
- Convert mixed units into one unit before comparing, adding, or subtracting.
- Convert the final answer back into friendly mixed units when useful.
- Check every answer by asking whether the size makes real-world sense.
1. Choose The Right Unit
Measurement is clearer when the unit matches the object. Very small lengths are easier in millimetres. Hand-sized lengths are often easier in centimetres. Room-sized lengths are usually easier in metres. Long distances between places are usually easier in kilometres.
The unit does not change the actual length; it changes how we write and read that length. A strip can be 78 mm or 7 cm 8 mm. Both describe the same strip. A path can be 1500 m or 1 km 500 m. Both describe the same path.
When a question gives only a number with a blank unit, think about the object. A pencil cannot be 180 kilometres long. A school corridor cannot be 18 millimetres long. Real-world sense is part of mathematical thinking.
Situation: A class note says a pencil is 180 long, a corridor is 18 long, and a road trip is 18 long.
- A pencil is small, so 180 millimetres is sensible.
- A corridor is room-sized, so 18 metres is sensible.
- A road trip is long, so 18 kilometres is sensible.
- The same number can feel different when the unit changes.
Answer: Pencil: 180 mm. Corridor: 18 m. Road trip: 18 km.
Choose a unit that gives a sensible number: mm for tiny lengths, cm for small objects, m for room-sized lengths, and km for long distances.
2. Use Unit Relationships
Unit conversion means writing the same length in a different unit. The main relationships in this chapter are simple but powerful: 10 mm = 1 cm, 100 cm = 1 m, and 1000 m = 1 km. Moving to a smaller unit makes the number larger because many small units fit inside one larger unit.
For example, 1 cm becomes 10 mm, and 7 cm becomes 70 mm. Moving to a larger unit makes the number smaller because the length is grouped into bigger units. For example, 935 cm contains 9 full metres, with 35 cm left.
A mixed length has two units, such as 6 m 25 cm. To calculate smoothly, convert it to one unit first. After calculation, you may convert the answer back into mixed units so it is easier to read.
Situation: A craft strip is 7 cm 8 mm long. Write its length only in millimetres.
- 1 cm = 10 mm.
- 7 cm = 7 x 10 = 70 mm.
- Add the extra 8 mm.
- 70 mm + 8 mm = 78 mm.
Answer: 7 cm 8 mm = 78 mm.
Situation: A ribbon roll has 935 cm of ribbon left. Write this as metres and centimetres.
- 100 cm = 1 m.
- 935 cm has nine full hundreds, so it has 9 m.
- After 900 cm, 35 cm remains.
- Keep the remainder in centimetres.
Answer: 935 cm = 9 m 35 cm.
3. Read Feet And Inches
Some rulers, measuring tapes, signs, and product labels use inches and feet. The short forms are in for inch and ft for foot. The relationship to remember is 1 ft = 12 in. Twelve inches grouped together make one foot.
A mixed measure such as 4 ft 7 in means four complete feet and seven more inches. To write it only in inches, multiply the number of feet by 12 and add the extra inches. To change inches back to feet and inches, make groups of 12. The quotient gives the feet and the remainder gives the inches.
Worked teaching example: 3 ft 5 in = (3 x 12) in + 5 in = 36 in + 5 in = 41 in. In the other direction, 50 in makes four groups of 12, with 2 in left, so 50 in = 4 ft 2 in.
Feet and inches belong to one unit family. Use 12, not 10 or 100, when changing between them.
4. Estimate Before Measuring
An estimate is a sensible near value, not a wild guess. Estimation helps you choose a unit, select a measuring tool, and notice an impossible answer. Build estimates from known references: the width of a finger is a few centimetres, a long classroom ruler may be about 1 metre, and the distance between towns is measured in kilometres.
Use a simple three-step method. First, choose a known reference. Second, imagine how many copies of that reference fit along the length. Third, measure and compare your estimate with the exact value. If a desk looks about the length of one metre ruler, you might estimate 1 m. If the measured length is 112 cm, the estimate was close because 112 cm is 1 m 12 cm.
Estimation example: A ribbon looks a little shorter than a 30 cm ruler. A sensible estimate is about 25 cm, not 25 m. If the exact measure is 27 cm, the estimate differs by only 2 cm. The difference tells you how close your estimate was.
Say both the estimated value and its unit. “About 25” is unfinished; “about 25 cm” is useful.
5. Compare Far And Near Lengths
To compare two lengths, put them in the same unit first. Comparing 620 cm and 6 m 15 cm is not fair until one side changes. Since 6 m 15 cm is 615 cm, we can compare 620 cm and 615 cm directly. Now it is clear that 620 cm is longer.
Near and far comparisons also need the same unit. Suppose the library is 450 m away, the clinic is 900 m away, and the park is 1 km 250 m away. Convert the park distance to 1250 m. Then the smallest number is nearest and the largest number is farthest.
Double number lines are a useful mental picture. One line can show metres, and another line can show centimetres. Matching points show equal measures, such as 2 m 35 cm and 235 cm.
Situation: Which is longer: 6 m 20 cm or 6 m 15 cm?
- Both lengths have 6 m.
- Compare the centimetre parts: 20 cm and 15 cm.
- 20 cm is greater than 15 cm.
- So the first length is longer.
Answer: 6 m 20 cm > 6 m 15 cm.
Do not compare only the first number. In 6 m 5 cm and 650 cm, the first number 6 looks similar, but 6 m 5 cm is 605 cm, not 650 cm.
6. Add And Subtract Lengths
Length addition and subtraction become safe when the units match. You can add metres with metres and centimetres with centimetres, or you can convert everything into the smaller unit first. The second method is often simpler for Class 5 because it avoids hidden regrouping.
For distance questions, convert kilometres and metres into metres. For cable, cloth, ribbon, or room lengths, convert metres and centimetres into centimetres. For tiny objects, convert centimetres and millimetres into millimetres.
After the calculation, convert the answer back if it helps the reader. An answer like 8250 m is correct, but 8 km 250 m is often friendlier for a walking-distance question.
Situation: A child walks 2 km 450 m in the morning and 5 km 800 m in the evening.
- Convert to metres: 2 km 450 m = 2450 m.
- Convert to metres: 5 km 800 m = 5800 m.
- Add: 2450 m + 5800 m = 8250 m.
- Convert back: 8250 m = 8 km 250 m.
Answer: The total walking distance is 8 km 250 m.
Situation: A safe classroom display needs 63 m 25 cm of string. The class has already used 16 m 40 cm.
- Convert both lengths to centimetres.
- 63 m 25 cm = 6325 cm.
- 16 m 40 cm = 1640 cm.
- 6325 cm – 1640 cm = 4685 cm.
- 4685 cm = 46 m 85 cm.
Answer: 46 m 85 cm of string is left.
7. Multiply And Divide Lengths
Multiply when the same length is repeated in equal groups. Divide when a total length is shared into equal pieces or when you need to know how many equal pieces fit. Convert to one unit before calculating so that every group uses the same kind of unit.
For multiplication, write length of one piece x number of pieces. For division, write total length / length of one piece. Check the inverse operation: a multiplication answer can be checked by dividing, and a division answer can be checked by multiplying.
Situation A: Five equal ribbons are each 1 m 25 cm long.
- Convert one ribbon: 1 m 25 cm = 125 cm.
- Multiply: 125 cm x 5 = 625 cm.
- Convert back: 625 cm = 6 m 25 cm.
Answer A: The five ribbons have a total length of 6 m 25 cm.
Situation B: A 9 m rope is cut into equal 75 cm pieces.
- Convert the total: 9 m = 900 cm.
- Divide: 900 / 75 = 12.
- Check: 12 x 75 cm = 900 cm.
Answer B: The rope makes 12 equal pieces.
8. Use Markers And Distance Patterns
Long paths often use repeated gaps: a sign every 250 m, a flag every 50 m, a rest point every 500 m, or a marker every 1 km. These questions combine measurement with multiplication and division.
First convert the total distance into the same unit as the gap. Then divide the total distance by the gap size. If the first marker is after the starting point, do not count the starting point as a marker. If the question says to mark both start and finish, then the start may also be counted. Read the wording carefully.
It helps to list the positions: 250 m, 500 m, 750 m, and so on. Listing prevents a common off-by-one error, where the start is counted even though no sign is placed there.
Situation: A 1 km 500 m practice path needs a sign every 250 m after the start.
- Convert the total distance: 1 km 500 m = 1500 m.
- Each sign is 250 m after the previous one.
- 1500 divided by 250 equals 6.
- The signs are at 250 m, 500 m, 750 m, 1000 m, 1250 m, and 1500 m.
Answer: 6 signs are needed after the starting point.
9. Measure Carefully And Safely
Good measurement is not only about formulas. The start point and end point must be clear. A ruler should begin at 0, not at the broken edge. A tape should be straight, not loose or bent. A walking-step estimate should be described as an estimate, not an exact distance.
When measuring tiny lengths such as sprouts, threads, paper strips, or craft pieces, millimetres give more precision than centimetres alone. But safety and hygiene matter. If you observe plant growth, do it with clean hands, safe seeds, and adult guidance. Do not taste anything as part of a maths activity.
For outdoor distances, use known safe spaces: a classroom floor, a school corridor with permission, or a marked playground area under adult supervision. Never cross roads, enter private spaces, or walk away from a trusted adult for a measurement task.
After every conversion, ask: did I move to a smaller unit or a larger unit? Smaller units should give a bigger number; larger units should give a smaller number.
Practice Time
Try each question before opening the answer.
Practice 1. Choose the better unit: the width of a fingernail is about 12 ___.
Answer: Millimetres, or mm.
Practice 2. Write 14 cm 6 mm only in millimetres.
Answer: 14 cm 6 mm = 146 mm.
Practice 3. Write 5 ft 8 in only in inches.
Answer: 5 x 12 + 8 = 68, so 5 ft 8 in = 68 in.
Practice 4. Write 3 km 750 m only in metres.
Answer: 3 km 750 m = 3750 m.
Practice 5. A shelf looks a little longer than a 1 m ruler. Which is the sensible estimate: 120 mm, 120 cm, or 120 km?
Answer: 120 cm, because 120 cm = 1 m 20 cm.
Practice 6. Compare using <, =, or >: 620 cm ___ 6 m 15 cm.
Answer: 6 m 15 cm = 615 cm, so 620 cm > 6 m 15 cm.
Practice 7. Four strips are each 75 cm long. What is their total length?
Answer: 75 x 4 = 300 cm = 3 m.
Practice 8. A rope is 50 m long. How many such ropes make 1 km?
Answer: 1 km = 1000 m, and 1000 / 50 = 20 ropes.
Practice 9. A sprout was 12 mm on Monday and 29 mm on Thursday. How much did it grow?
Answer: 29 mm – 12 mm = 17 mm.
Practice 10. Add 4 km 620 m and 2 km 780 m.
Answer: 4620 m + 2780 m = 7400 m = 7 km 400 m.
Quick Self-Check
Use these five to test the main ideas.
Self-check 1. How many millimetres are in 1 centimetre?
Answer: 10 millimetres.
Self-check 2. How many centimetres are in 1 metre?
Answer: 100 centimetres.
Self-check 3. How many metres are in 1 kilometre?
Answer: 1000 metres.
Self-check 4. Why is 2 km usually easier to read than 2000 m for a town distance?
Answer: Because kilometre is the friendlier unit for long distances.
Self-check 5. What should you do before adding 3 m 75 cm and 2 m 50 cm?
Answer: Use like units, or convert both to centimetres first.
Small Step: Measure one safe object today, convert it into a smaller unit, and check whether the new number makes sense.
Continue Learning
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- Explore Class 5 Mathematics guides
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