RRB NTPC Mains or Stage 2 Model Paper 2 with solutions

Question : 20 of 120

Marks: +1, -0

Find the fourth proportional to 12, 18, 20.

Solution:

(a) Let fourth proportional is x.
Then,
12 : 18 : : 20 : x

⇒12/18= 20/x⇒x={ 18 ×20 }/12=30.

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