NCERT Solutions for Class 5th Maths Chapter 5 Saji's walk and the electricians' cable — Adding and Subtracting Lengths
Book page 64–65 Updated on2026-09-19
Q1.
Saji saw on his smartphone that he walked 3 km 450 m in the morning and another 4 km 650 m in the evening. How much did he walk in the whole day? How would you solve this problem? Share your thoughts in class.
Answer
Saji walked 8 km 100 m in the whole day.
There are two good ways. Both give the same answer — use whichever you like.
Way 1 — add like units together.
Add the kilometres. 3 km + 4 km = 7 km.
Add the metres. 450 m + 650 m = 1,100 m.
1,100 m is more than a kilometre, so change it: 1,100 m = 1 km 100 m.
Put the pieces together. 7 km + 1 km 100 m = 8 km 100 m.
Way 2 — change everything into metres first.
3 km 450 m = 3,000 + 450 = 3,450 m.
4 km 650 m = 4,000 + 650 = 4,650 m.
Add. 3,450 + 4,650 = 8,100 m.
Change back. 8,100 m = 8,000 m + 100 m = 8 km 100 m.
Way 1: 7 km + 1,100 m = 7 km + 1 km 100 m = 8 km 100 m Way 2: 3,450 m + 4,650 m = 8,100 m = 8 km 100 m Both ways agree ✓
Adding two lengths means laying them end to end.
Why 1,100 m had to be changed: We do not leave an answer as "7 km 1,100 m", just as we do not leave 15 rupees as "1 ten and 5 ones and 10 more ones". Once the metres reach 1,000 they make a whole kilometre, and that kilometre joins the kilometre column.
Sample answer for the class discussion: "I liked Way 2 better, because once everything is in metres it is just an ordinary addition sum like 3,450 + 4,650. Way 1 is quicker in the head when the metres add up to less than 1,000."
Q2.
Electricians are changing the cables in a house. They need 63 m of cable for this purpose. They used 16 m 75 cm cable in the first room. What is the length of the cable left?
Answer
46 m 25 cm of cable is left.
We must find what is left, so we subtract. First name the two quantities.
Cable they started with: 63 m
Cable already used: 16 m 75 cm
Change both into centimetres, then subtract.
63 m = 63 × 100 = 6,300 cm.
16 m 75 cm = 1,600 + 75 = 1,675 cm.
Subtract. 6,300 − 1,675 = 4,625 cm.
Change back into metres. 4,625 = 4,600 + 25, and 4,600 cm = 46 m. So the answer is 46 m 25 cm.
6,300 cm − 1,675 cm ——————————— 4,625 cm
4,625 cm = 4,600 cm + 25 cm = 46 m 25 cm
You can also subtract in two columns, metres and centimetres, exactly as the book shows. Because 0 cm is less than 75 cm, borrow one metre and turn it into 100 cm.
m
cm
Start with
63 → 62
00 → 100
Take away
16
75
Left
46
25
Why we borrow 100 and not 10: When we borrow in ordinary subtraction, one ten becomes 10 ones. Here, one metre becomes 100 centimetres — because that is how many centimetres a metre holds. The borrowing rule always follows the unit.
Check it yourself: Add back. 46 m 25 cm + 16 m 75 cm = 62 m and 100 cm = 63 m ✓ That is exactly the cable they started with.