A sprinter starts running on a circular path of radius r metres.Her average speed(metres/minutes) is (pie)*r?

Question

A sprinter starts running on a circular path of radius r metres.Her average speed(metres/minutes) is (pie)*r during the first 30 seconds,(pie)*r/2 during the next one minute,(pie)*r/4 during next 2 minutes,(pie)*r/8 during next 4 minutes and so on.What is the ratio of the time taken for the nth round to that for the previous round.
(a) 8:9
(b) 9:10
(c) 10:11
(d) 11:12
pie means 22 / 7

Answer 1

the answer is 16:1, that is not one of your choices

Answer 2

" What is the ratio of the time taken for *** the nth round *** to that for the previous round."

in each period she runs 1/4 of a circle so the first circle is done in
0.5 + 1 + 2 + 4 minutes = 7.5 mninutes

the next round :
8 + 16 + 32 + 64 minutes

next round
128 + 256 + 512 + 1024 minutes

as you can see the ration is not constant but depends on n.

so none of the answers is correct.


uhh just wact backtonature told you.

Answer 3

Unless I understood wrongly, else none of the above.
The sprinter is running slower and slower, thus the nth round should take longer than the previous round!

Also, I don't see the need for the info pi = 22/7.

At each speed, she covers a quarter of a round,
1st round: she spent 0.5+1+2+4 = 7.5 mins
2nd round: she spent 8+16+32+64 = 120 mins.
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