Question 43442
Let us suppose that the school purchased 'x' bulbs, each costing $2.
As the school purchased twice as many $1.00 bulbs as it did $2.00 bulbs, so it must have purchased '2x' bulbs, each costing $1.


Cost of all $1 bulbs = $1 x (no. of $1 bulbs purchased) = ${{{1*2x}}} = $2x.
Cost of all $2 bulbs = $2 x (no. of $2 bulbs purchased) = ${{{2*x}}} = $2x.
Total cost of all bulbs = $2x + $2x = $4x.
Given: total cost of all bulbs = $600.


So, 4x = 600 or x = {{{600/4}}} = 150.


Hence the answer.