Out of 40 bulbs, 3 were faulty.
3/40 were faulty
out of 500 bulbs, 'x' were faulty.
x/500 were faulty
\(\frac{3}{40} = \frac{x}{500}\)
cross multiply
40x=1500
Divide both sides by 40
x=37.5
Since you can't have .5 of a bulb, lets round up to 38
Answer=38 bulbs
