NCERT Solutions for Class 4th Maths Chapter 6 Measuring Small Things — Let Us Observe
Book page 84 Updated on2026-09-19
Q1.
Can you think how to measure a small thing like an eraser or a rice grain?
Answer
Yes. We use a smaller unit called the centimetre (cm), and a scale.
A metre rope is far too big for a rice grain. So we look at a standard metre scale.
The metre scale is divided into 100 equal parts.
The length of each one of those parts is called one centimetre (cm).
Put the thing on the scale so that one end is exactly at 0, and read the number at the
other end.
A 0 to 10 scale. The gap between two marks next to each other is one centimetre.
1 metre (m) = 100 centimetre (cm)
Why it happens: A small thing needs a small unit. If the unit is bigger than
the thing, the answer is always “less than one”, which tells us nothing.
Q2.
Compare the metre rope with the measuring tape used by a tailor. Is the length of both the same or different?
Answer
The 1 m rope and the tailor’s tape laid one below the other.
Their length is the same. Both are 1 m long.
Metre rope = 1 m
Tailor's measuring tape = 1 m = 100 cm
The difference is not the length. It is what is written on them:
The rope is plain. It can only tell us “one whole metre”.
The tape has marks and numbers. It can also tell us 1 cm, 7 cm, 45 cm and so on.
Why it happens: The tape is a metre rope that has been cut into 100 equal
parts with marks. The total length does not change when we mark it.
Q3.
Observe the measuring tape carefully. What do you notice?
Answer
The measuring tape on page 84, with its marks and numbers.
These are the things we notice on the tape:
It has many small marks along one edge.
Numbers are written beside the marks: 0, 1, 2, 3 … 10 and further.
The counting starts at 0, not at 1.
All the gaps are equal. The gap between two marks next to each other is
1 cm.
The red bar in the book is exactly one such gap, so one red bar is 1 cm.
The red bar repeated 10 times makes 10 cm, and repeated 100 times makes 1 m.
Why it happens: Measuring is counting equal gaps. That is why the gaps on a
tape must all be the same size.
Tip: The number 100 on a metre tape does not mean 100 marks. It means the
distance from 0 is 100 gaps of 1 cm each.
Q4.
Discuss how these marks help us measure clearly.
Answer
The marks on the tape cut one metre into 100 equal pieces.
The marks help us in three ways:
They cut the tape into equal pieces of 1 cm, so everyone gets the same answer.
We do not have to count the pieces one by one. The number beside the mark tells us how
many centimetres we have already covered.
They let us say a length exactly — 7 cm, not just “a little less than my
hand”.
Without marks: “the pencil is about two fingers long”
With marks: the pencil is 10 cm long
Why it happens: Fingers, hands and footsteps are different for every child.
A centimetre is the same for everybody, so the marks make our answers match.
Q5.
1/2 m = _____ cm, 1/4 m = _____ cm
Answer
1/2 m = 50 cm and 1/4 m = 25 cm.
1 m = 100 cm
1 m = 1/2 m + 1/2 m
50 + 50 = 100 → 1/2 m = 50 cm
1 m = 1/4 m + 1/4 m + 1/4 m + 1/4 m
25 + 25 + 25 + 25 = 100 → 1/4 m = 25 cm
The 1 m rope, the two half-metre ropes and the four quarter-metre ropes.
Why it happens: The half-metre rope is half of the metre rope, so it must be
half of 100 cm. The quarter-metre rope is half of the half, so it is half of 50 cm.
Check it yourself: 25 + 25 = 50, and 50 + 50 = 100. The ropes fit
together exactly.