NCERT Solutions for Class 5th Maths Chapter 5 Relationships between Different Units — Let Us Do
Book page 63–64 Updated on2026-09-19
Q1.
Fill in the blanks appropriately in the double number lines given below. (a) top: 1 cm, 7 cm, 15 cm, ___ cm, ___ cm, ___ cm, 50 cm; bottom: 10 mm, ___ mm, ___ mm, 250 mm, 320 mm, 450 mm, ___ ; and the multiplier boxes ×7, ×10, ×__, ×__. (b) top: 1 m, 4 m, 10 m, ___ m, ___ m, ___ m, 21 m; bottom: ___ cm, ___ cm, ___ cm, 1,200 cm, 1,400 cm, 1,700 cm, ___ cm; boxes ×4, ×100, ×__, ×__. (c) top: 1 km, 9 km, 25 km, ___ km, ___ km, ___ km, 82 km; bottom: 1,000 m, ___ m, ___ m, 41,000 m, 55,000 m, 67,000 m, ___ m; boxes ×9, ×1,000, ×__, ×__.
Answer
On a double number line, the two lines are lined up tick for tick. Going down or up between the lines changes the unit. Going sideways along a line changes the length.
(a) centimetres and millimetres — 1 cm = 10 mm
(a) filled in. Red is what you write. Both empty boxes are ×10 and ×7.
7 cm = 7 × 10 = 70 mm · 15 cm = 150 mm 250 mm = 250 ÷ 10 = 25 cm · 320 mm = 32 cm · 450 mm = 45 cm 50 cm = 50 × 10 = 500 mm Empty boxes: the one below 7 cm is ×10, the bottom one is ×7
A misprint to know about: The very last label on the bottom line of (a) is printed as "____ m". It should be "____ mm", because that whole line is in millimetres. The answer is 500 mm. (500 mm is only half a metre, so "m" cannot be right.)
(b) metres and centimetres — 1 m = 100 cm
Top line (m)
1 m
4 m
10 m
12 m
14 m
17 m
21 m
Bottom line (cm)
100 cm
400 cm
1,000 cm
1,200 cm
1,400 cm
1,700 cm
2,100 cm
Both empty boxes: the one under 4 m is ×100, the bottom one is ×4 1 m = 1 × 100 = 100 cm · 4 m = 400 cm · 10 m = 1,000 cm 1,200 cm = 1,200 ÷ 100 = 12 m · 1,400 cm = 14 m · 1,700 cm = 17 m 21 m = 21 × 100 = 2,100 cm
(c) kilometres and metres — 1 km = 1,000 m
Top line (km)
1 km
9 km
25 km
41 km
55 km
67 km
82 km
Bottom line (m)
1,000 m
9,000 m
25,000 m
41,000 m
55,000 m
67,000 m
82,000 m
Both empty boxes: the one under 9 km is ×1,000, the bottom one is ×9 9 km = 9 × 1,000 = 9,000 m · 25 km = 25,000 m 41,000 m = 41,000 ÷ 1,000 = 41 km · 55,000 m = 55 km · 67,000 m = 67 km 82 km = 82,000 m
The one idea behind all three: Going down to the smaller unit means multiplying — by 10 for cm to mm, by 100 for m to cm, by 1,000 for km to m. Going up to the bigger unit means dividing by the same number. The smaller the unit, the more of them you need, so the number gets bigger.
Quick trick with zeros: ×10 adds one zero, ×100 adds two zeros, ×1,000 adds three zeros. 82 km → 82,000 m. And going the other way, take the zeros off: 25,000 m → 25 km.
Q2.
Use your understanding from above to fill in the blanks appropriately. (a) 4 cm 5 mm = ____ mm (b) 89 mm = ____ cm ____ mm (c) 234 cm = ____ mm (d) 514 mm = ____ cm ____ mm (e) 6 m 34 cm = ____ cm (f) 20 m 12 cm = ____ cm (g) 397 m = ____ cm (h) 5,792 cm = ____ m ____ cm (i) 9,108 cm = ____ m ____ cm (j) 34 km = ____ m (k) 6,870 m = ____ km ____ m (l) 10,552 m = ____ km ____ m (m) 29 km 30 m = ____ m (n) 32 km 359 m = ____ m
Answer
Keep three facts in front of you: 1 cm = 10 mm, 1 m = 100 cm, 1 km = 1,000 m.
Part
Answer
Working
(a) 4 cm 5 mm
45 mm
4 cm = 40 mm; 40 + 5 = 45
(b) 89 mm
8 cm 9 mm
89 = 80 + 9; 80 mm = 8 cm
(c) 234 cm
2,340 mm
234 × 10 = 2,340
(d) 514 mm
51 cm 4 mm
514 = 510 + 4; 510 mm = 51 cm
(e) 6 m 34 cm
634 cm
6 m = 600 cm; 600 + 34 = 634
(f) 20 m 12 cm
2,012 cm
20 m = 2,000 cm; 2,000 + 12 = 2,012
(g) 397 m
39,700 cm
397 × 100 = 39,700
(h) 5,792 cm
57 m 92 cm
5,792 = 5,700 + 92; 5,700 cm = 57 m
(i) 9,108 cm
91 m 8 cm
9,108 = 9,100 + 8; 9,100 cm = 91 m
(j) 34 km
34,000 m
34 × 1,000 = 34,000
(k) 6,870 m
6 km 870 m
6,870 = 6,000 + 870
(l) 10,552 m
10 km 552 m
10,552 = 10,000 + 552
(m) 29 km 30 m
29,030 m
29 km = 29,000 m; 29,000 + 30
(n) 32 km 359 m
32,359 m
32 km = 32,000 m; 32,000 + 359
There are only two kinds of question here, and each has its own recipe.
Recipe 1 — big unit into small unit (parts a, c, e, f, g, j, m, n):
Change the big part by multiplying (×10, ×100 or ×1,000).
Add the small part that was already there.
Recipe 2 — small unit into big unit (parts b, d, h, i, k, l):
Split the number into a round part and a leftover: 5,792 = 5,700 + 92.
The round part changes into whole big units: 5,700 cm = 57 m.
The leftover stays as it is: 92 cm.
Why the split works: 5,700 cm is exactly 57 hundreds of centimetres, and each hundred is one metre. The 92 left over is not enough to make another whole metre, so it stays in centimetres.
Watch part (i): 9,108 cm = 91 m 8 cm, not 91 m 80 cm. Look at the last two digits — they are 0 and 8, which is eight, not eighty.
Check any answer by going back: Part (l) says 10,552 m = 10 km 552 m. Check: 10 km = 10,000 m, and 10,000 + 552 = 10,552 ✓