Mathematics question?

Question

Every 5 seconds,half of the water in a cistern empties out into a drain. If the cistern were fullto start with, what fraction of the cistern will still contain water after 25 seconds?
A 1/2 B 1/32 C 1/8 D 1/16

Answer 1

After 1 second, you'd have 1/2 of 1, or 1/2.

After 2 seconds, you'd have 1/2 of 1/2, or 1/4.

After 3 seconds, you'd have 1/2 of 1/4, or 1/8.

After 4 seconds, you'd have 1/2 of 1/8, or 1/16.

After 5 seconds, you'd have 1/2 of 1/16, or 1/32.

(1/2)^5 = 1/2 x 1/2 x 1/2 x 1/2 x 1/2 = 1/32, answer B.

Answer 2

After 5 seconds 1/2 of the water will be gone. Five seconds later half the remaining water or 1/4 of the capacity will remain. Five seconds later 1/2 the remaining water has gone and 1/8 or the tank remains. Half again in the next five seconds and we're down to 1/16. At then end of the remaining five seconds, 1/32 of the original amount will remain.

Answer 3

In 5 secs, it is 1/2 of the total volume of water.
So,
5 sec = 1/2
10 secs = 1/2 divided by 2
15 secs = 1/4 divided by two again
and so on, so it is (1/2)^5 because 25 secs is 5 times of it.

*1/4 because 1/2 divide by 2 = 1/2 x 1/2 = 1/4

So, the answer is 1/32 ( 1/ 2x2x2x2x2 = 1 / 32)

Answer 4

1/2 x 1/2 x 1/2 x 1/2 x 1/2 = 1/32

Answer 5

B....But, consider IF one half of the total water drained in 5 seconds, it would be empty in 11 seconds.

Answer 6

5 50%
10 25%
15 12.5%
20 6.25%
25 3.125% = 1/32

Answer 7

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