NCERT Solutions for Class 5th Maths Chapter 12 Observe the clocks and fill in the blanks — Let Us Do
Book page 159 Updated on2026-09-19
Q1.
Observe the clocks and fill in the blanks. (1) Rani took ______ sec. to get out of her bed.
Answer
Rani took 30 seconds.
Both clocks have three hands. Only the thin red seconds hand has moved, so we only have to look at that one.
Left clock: 6:45 and 0 seconds. Right clock: 6:45 and 30 seconds. Only the red hand has shifted.
First clock. The red hand is on 12. That means 0 seconds.
Second clock. The red hand is on 6. Count in fives from 12: 5, 10, 15, 20, 25, 30. So 30 seconds.
Subtract. 30 − 0 = 30.
End reading = 30 seconds Start reading = 0 seconds Time taken = 30 − 0 = 30 seconds
Tip: On the seconds hand, each big number is worth 5 seconds, exactly like the minute hand. 12 → 0 s, 3 → 15 s, 6 → 30 s, 9 → 45 s. Half a round is 30 seconds.
Q2.
(2) Raghav took ______ sec. to move from his room to the kitchen.
Answer
Raghav took 35 seconds.
Left clock: 4:45 and 0 seconds. Right clock: 4:45 and 35 seconds.
First clock: red hand on 12 → 0 seconds.
Second clock: red hand on 7. Count in fives: 5, 10, 15, 20, 25, 30, 35. So 35 seconds.
Subtract: 35 − 0 = 35.
35 seconds − 0 seconds = 35 seconds
Why the minute hand did not move: The minute hand shifts to the next small mark only after a whole 60 seconds. Raghav took just 35 seconds, so the seconds hand had not finished its round yet and the green hand stayed on 9.
Q3.
(3) Ritu took ______ sec. to pick up a piece of paper from the floor.
Answer
Ritu took 15 seconds.
This one is different — the seconds hand crosses the 12 while she is bending down, so read it carefully.
Left clock: the red hand is on 9, which is 45 seconds. Right clock: the red hand is back on 12, which is a full 60 seconds.
First clock: red hand on 9. Count in fives: 5, 10, 15, 20, 25, 30, 35, 40, 45. So 45 seconds.
Second clock: red hand on 12. It has gone all the way round to the end of that minute, so this is 60 seconds.
Subtract: 60 − 45 = 15.
60 seconds − 45 seconds = 15 seconds
Why we call the second reading 60 and not 0: The red hand did not stand still — it carried on from 45 to the top of the dial. Those last marks are 46, 47, 48 … right up to 60. Once it touches 12 the minute is complete, and only then does the counting start again from 0.
Count it another way: From 9 to 10 is 5 seconds, 10 to 11 is 5 seconds, 11 to 12 is 5 seconds. 5 + 5 + 5 = 15 seconds.
Q4.
(4) Raghu took ______ sec. to wash his spoon and plate.
Answer
Raghu took 60 seconds, that is 1 whole minute.
At first the two clocks look exactly the same — the red hand is on 5 in both. The clue is hidden in the green minute hand.
The red hand is on 5 in both clocks. But look at the green minute hand — it has slipped forward by one small mark.
First clock: green hand on 12, red hand on 5 → 25 seconds past six o'clock.
Second clock: the red hand is again on 5, so again 25 seconds. But the green hand has moved on by one small mark.
What one small mark means. The minute hand moves one small mark only when the seconds hand has gone once fully round.
So the seconds hand made one full round. One full round = 60 seconds.
One full round of the seconds hand = 60 seconds = 1 minute Raghu took 60 seconds
Why the seconds hand alone is not enough: The seconds hand comes back to the same place every single minute. So the same red position can mean 25 seconds, or 1 minute 25 seconds, or 2 minutes 25 seconds. To know how many whole minutes have gone, you must look at the minute hand as well.
Check it yourself: Count the seconds hand's journey — 25 → 30 → 45 → 60 → 0 → 25. That is 35 seconds to reach the top and 25 seconds after it. 35 + 25 = 60 seconds ✓