Question

If (10x + 5) : (42x + 8) is the triplicate ratio for 5 : 8, find x³
1. 1,000
2. 1,331
3. 1,728
4. 2,197

Answer 1

Correct Answer - Option 3 : 1,728

Given : 

(10x + 5) : (42x + 8) = 5 : 8 

Concept used :

x: y = a : b 

Triplicate ratio for a : b will be 

x : y = a³ : b³ 

Calculations :

(10x + 5) : (42x + 8) = 5³ : 8³ (triplicate ratio for 5 : 8)

⇒ (10x + 5) : (42x + 8) = 125 : 512 

⇒ x = 12 

⇒ (x)³ = 12³

⇒ 1728 

∴ the value of x will be 1728