Question

On selling 10 watches at Rs. 1400 there is a loss equal to the cost price of 3 watches. Find the cost price of a watch.

Answer 1

Let the C.P. of 3 watches be Rs. x.

∴ C.P. of 1 watch
= Rs.`x/(3)`

⇒ C.P. of 10 watches
= Rs.`(10x)/(3)`
Loss on selling 10 watches
= C.P. of 3 watches
= Rs.x
S.P. of 10 watches is Rs.1400
Loss incurred on selling 10 watches
= C.P. of 3 watches
= Rs.x
Since C.P. - S.P. = Loss
⇒ Rs.`(10x)/(3) - "Rs".1400`
= Rs.x

⇒ `(10x - 4200)/(3)` = x

⇒ 10x - 4200 = 3x
⇒  7x = 4200
⇒  x = 600

Hence, C.P. of a watch
= Rs.`x/(3)`

= Rs.`(600)/(3)`
= Rs.200.