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NCERT Solutions for Class 5th Maths Chapter 12 Zainab and Remo, and the hours-and-minutes double number line — Conversion of Hours to Minutes

Book page 161 Updated on2026-09-19

Q1.
Use the double number line below to complete the conversions.
1 hr60 min___ hr120 min4 hr___ min7 hr___ min__ hr480 min9 hr___ min___ hr660 min___ hr720 min× 2
Page 161, Question 1 (a) — the double number line. Hours on the top line, minutes on the bottom line.
Answer

Here is the completed double number line. The answers are shown in red.

hours minutes 12 47 89 1112 60120 240420 480540 660720
Every hour on the top line sits directly above its number of minutes on the bottom line.
HoursWorkingMinutes
1 hr1 × 6060 min
2 hr2 × 60120 min
4 hr4 × 60240 min
7 hr7 × 60420 min
8 hr8 × 60480 min
9 hr9 × 60540 min
11 hr11 × 60660 min
12 hr12 × 60720 min

How to fill any blank on this line:

  1. Blank on the bottom (minutes missing): take the hours above it and multiply by 60. For 4 hr → 4 × 60 = 240 min.
  2. Blank on the top (hours missing): take the minutes below it and divide by 60. For 480 min → 480 ÷ 60 = 8 hr.
4 × 60 = 240    7 × 60 = 420    9 × 60 = 540
480 ÷ 60 = 8    660 ÷ 60 = 11    720 ÷ 60 = 12
120 ÷ 60 = 2
Why the line is drawn twice: The same moment of time can be named in two ways — as hours or as minutes. Drawing them one above the other lets you slide from one name to the other without any calculation at all. Just look straight up, or straight down.
Check it yourself: 12 hours is half a day, and 720 minutes is what our line says. Test it: 720 ÷ 60 = 12 ✓ Two of these make 1440 minutes, which is one whole day.
Q1.
Do as instructed. You can use the double number line below.
1 hr60 min___ hr120 min4 hr___ min7 hr___ min__ hr480 min9 hr___ min___ hr660 min___ hr720 min× 2
Page 161 — the double number line from Question 1 (a). Hours on the top line, minutes on the bottom line.

(i) 1 hours 10 minutes = _____ minutes

Answer

70 minutes.

  1. Split it into two pieces: 1 hour, and 10 minutes.
  2. Change the hour piece into minutes: 1 hour = 60 minutes.
  3. Add the loose minutes: 60 + 10 = 70.
1 hour 10 minutes
= 60 min + 10 min
= 70 minutes
On the number line: find 1 hr on the top; below it is 60 min. Then step 10 more minutes along the bottom line. You land on 70.
Q1.
(ii) 2 hours 45 minutes = _____ minutes
Answer

165 minutes.

  1. Split: 2 hours, and 45 minutes.
  2. Hours into minutes: 2 × 60 = 120 minutes.
  3. Add: 120 + 45 = 165.
2 hours 45 minutes
= (2 × 60) + 45
= 120 + 45
= 165 minutes
Check it yourself: 165 − 120 = 45, and 120 ÷ 60 = 2. So 165 minutes really is 2 hours 45 minutes ✓
Q1.
(iii) 3 hours 15 minutes = _____ minutes
Answer

195 minutes.

  1. Split: 3 hours, and 15 minutes.
  2. Hours into minutes: 3 × 60 = 180 minutes. (This is exactly what Remo says on page 161.)
  3. Add: 180 + 15 = 195.
3 hours 15 minutes
= (3 × 60) + 15
= 180 + 15
= 195 minutes
Q1.
(iv) 4 hours 20 minutes = _____ minutes
Answer

260 minutes.

  1. Split: 4 hours, and 20 minutes.
  2. Hours into minutes: 4 × 60 = 240 minutes. You can read this straight off the double number line.
  3. Add: 240 + 20 = 260.
4 hours 20 minutes
= (4 × 60) + 20
= 240 + 20
= 260 minutes
The pattern in (i) to (iv): hours × 60, then add the loose minutes. That one rule does all four.
Q1.
(v) 75 minutes = ____ hour ____ minutes
Answer

1 hour 15 minutes.

Now we go the other way, so we take out whole hours instead of putting them in.

  1. Ask: how many whole 60s are hiding in 75? Just one, because 60 fits into 75 once and 120 would be too big.
  2. Take out that hour: 75 − 60 = 15.
  3. Name the two pieces: 1 hour, and 15 minutes left over.
75 ÷ 60 → 1 hour, remainder 15
75 minutes = 1 hour 15 minutes
Why we divide by 60 and not by 100: An hour is not made of a hundred minutes. It is made of sixty. So when we bundle loose minutes into hours, we bundle them sixty at a time.
Q1.
(vi) 150 minutes = ____ hours ____ minutes
Answer

2 hours 30 minutes.

  1. How many whole 60s are in 150? 60 + 60 = 120, and one more 60 would make 180, which is too big. So 2 hours.
  2. Take them out: 150 − 120 = 30.
  3. So 150 minutes = 2 hours 30 minutes.
150 ÷ 60 → 2 hours, remainder 30
150 minutes = 2 hours 30 minutes
Check it yourself: (2 × 60) + 30 = 120 + 30 = 150 ✓ Working backwards is the best way to be sure.
Q1.
(vii) 220 minutes = ____ hours ____ minutes
Answer

3 hours 40 minutes.

  1. Look at the number line. The nearest hour mark below 220 minutes is 180 minutes, which is 3 hours. (240 minutes would be 4 hours — too big.)
  2. Take out those 3 hours: 220 − 180 = 40.
  3. So 220 minutes = 3 hours 40 minutes.
220 ÷ 60 → 3 hours, remainder 40
220 minutes = 3 hours 40 minutes
Check it yourself: (3 × 60) + 40 = 180 + 40 = 220 ✓
Q1.
(viii) 390 minutes = ____ hours ____ minutes
Answer

6 hours 30 minutes.

  1. Count 60s up to 390: 60, 120, 180, 240, 300, 360. That is six 60s. The next one, 420, is bigger than 390.
  2. So there are 6 whole hours inside 390 minutes.
  3. Take them out: 390 − 360 = 30.
  4. So 390 minutes = 6 hours 30 minutes.
390 ÷ 60 → 6 hours, remainder 30
390 minutes = 6 hours 30 minutes
Check it yourself: (6 × 60) + 30 = 360 + 30 = 390 ✓ That is a long school day — from 8 in the morning to half past two.
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