A rope can make 70 rounds of the circumference of a cylinder whose radius of the base is 14cm. how many times can it go round a cylinder having radius 20 cm?
Options: A) 49 rounds B) 42 rounds C) 54 rounds D) 52 rounds E) none of these

Rationale: explanation : let the required number of rounds be x more radius , less rounds ( indirect proportion ) hence we can write as radius 14 : 20 } : : x : 70 ⇒ 14 × 70 = 20 x ⇒ 14 × 7 = 2 x ⇒ x = 7 × 7 = 49 . answer : option a
Answer: A