NCERT Solutions Ganita Prakash (Part 1) Chapter 3 In-text Questions — Units of Measurement
Book page 66 Updated on2026-09-05
Q1.
How many m is (a) 10 cm? (b) 15 cm?
Answer
1 m = 100 cm, so 1 cm = 1⁄100 m = 0.01 m
(a) 10 cm = 10⁄100 m = 1⁄10 m = 0.1 m
(b) 15 cm = 15⁄100 m = 10⁄100 m + 5⁄100 m = 1⁄10 m + 5⁄100 m = 0.15 m
Why it happens: each centimetre is one-hundredth of a metre, so a number of centimetres is that many hundredths of a metre. 15 hundredths regroups as 1 tenth and 5 hundredths, which is written 0.15.
Q2.
Fill in the blanks below (cm <–> m): 36 cm = _______; 50 cm = _______; _______ = 0.89 m; 4 cm = _______; 325 cm = _______; ________ = 2.07 m
Answer
Given
Working
Answer
36 cm
36⁄100 m
0.36 m
50 cm
50⁄100 m
0.5 m
? = 0.89 m
0.89 × 100
89 cm
4 cm
4⁄100 m
0.04 m
325 cm
325⁄100 m = 3 m + 25⁄100 m
3.25 m
? = 2.07 m
2.07 × 100
207 cm
Why it happens: cm → m divides by 100 (decimal point two steps left) and m → cm multiplies by 100 (two steps right). Note 4 cm = 0.04 m, not 0.4 m — the zero in the tenths place must be written.
Q3.
How many mm does 1 meter have?
Answer
1 m = 100 cm 1 cm = 10 mm 1 m = 100 × 10 = 1000 mm
Why it happens: the metre is split into 100 centimetres and each of those into 10 millimetres, giving 100 groups of 10 — one thousand millimetres in all.
Q4.
Can we write 1 mm = 1/1000 m?
Answer
Yes.
1 m = 1000 mm So 1 mm = 1⁄1000 m = 0.001 m
Why it happens: a thousand equal millimetres fill one metre, so each one is one-thousandth of a metre. That is exactly the third decimal place, which is why 1 mm is written 0.001 m.
Tip: the prefix "milli-" itself means one-thousandth: millimetre, milligram, millilitre.