Question

A school has 8 periods a day each of 45 minutes duration. How long would each period be, if the school has 9 periods a day, assuming the number of school hours to be the same ?

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Correct option is

Hence, the number of periods per day and the duration of each period are in inverse proportion.

Let the duration of each period if there are $9$ periods per day, be $aminutes$

Then, $8:9::$ inverse ratio of $45:a$

$=>8:9=a:45$

Applying the rule, product of extremes $=$ product of means

$8×45=9×a$

$a=98×45 $

$a=40$

Hence, if there are $9$ periods, the duration of each period is $40$ minutes.

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