PS - Light Bulbs

[mavesum]

A number of light bulbs were purchased to illuminate a gym. However, only 2/3 of them were needed and 160 leftover light bulbs were returned. If only 60% of their cost, or $96, was reimbursed, how much money was spent on illuminating the gym?

Ans :

SPOILER: 384$

[rajatmeh]

1/3 bulbs were returned = 160 bulbs
==> 2/3 bulbs consumed = 2*160 = 320
60% of (cost of 160 bulbs) = 96
==> cost of 160 bulbs = 160
==> cost of 1 bulb = 1
40% of (cost of 160 bulbs) = 160*1*40/100=64 ---(i)

Cost of 2/3 bulbs = 1*320=320 ---(ii)

(i) + (ii) = 384

[neuroticA]

let n be the total no of bulbs

bulb used-2/3x bulb returned-1/3x

x/3=160 or x=480

let c be the cost of each bulb

cost of 160 bulbs =160c

amount reimbersed - .60*160c=96 or c=1

Total cost= 160*.40+ 320*1= 384

[mavesum]

Thanks guys .