The fourth proportional to 5, 35 and x is 84, find the value of x.
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 12.
Fourth proportional to a, b, c is d, if:
a : b = c : d
Given: 5 : 35 = x : 84
Cross-multiply:
5 × 84 = 35 × x
420 = 35x
x = 420 ÷ 35 = 12