Solution -
Let,
The third proportion = x.
so,
21, 42 and x be in continued proportion.
Therefore,
21 : 42 :: 42 : x
21/42 = 42/x
1/2 = 42/x
x = 84
Thus,
The third proportion is 84.
Now,
Let,
Mean proportion = y
so,
16, y and 49 be in continued proportion.
Therefore,
16 : y :: y : 49
16/y = y/49
16 × 49 = y²
y² = 16 × 49
y = squareroot of 16 × 49
y = (16 × 49)½
y = 4 × 7
y = 28
Thus,
The Mean proportion is 28.
Therefore,
Requried ratio = 84 : 28
= 3 : 1
The ratio of third proportional to 21 and 42 and mean proportional to 16 and 49 is 3 : 1.
Hence,
The correct answer is option (a) 3 : 1.
Thank YouDownload App for Free PDF Download
GovtVacancy.Net Android App: Download |