Question

An electric kettle has two coils of same power . When one coil is switched on , it takes `15 min` to boil water , and when the second coil is switched on , it takes `30 min`. How long will it take to boil water when both the coils are used in `i`. Series and `ii`. parallel?
A. `9:2`
B. `2:9`
C. `4:5`
D. `5:4`

Answer 1

Correct Answer - A
`t_(S)=t_(1)+t_(2),t_(P)=(t_(1)t_(2))/(t_(1)+t_(2))`