Find two numbers such that their mean proportional is 6 and third proportional is 20.25.

A 4 and 9

B 3 and 5

C 5 and 7

D 2 and 5

Solution

Correct Answer: Option A

সংখ্যাদ্বয় x ও y
অতএব ,x/6=6/y
বা,xy=36
x=36/y.........(i)
আবার x/y =y/20.25
বা,(36/y)/y =y/20.25
বা,36/y²=y/20.25
বা,y³=729
বা,(y)³=9³
বা,y=9
অতএব, (i)
    x=36/9=4
অতএব ,সংখ্যাদ্বয় 4 ও 9

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