In David's class, 3/5 of the boys build model rockets to launch. Instead of parachutes, streamers were used on 2/9 of the Rockets, to slow them down. What fraction of the boys build rockets that had streamers?

So 3/5 of boys had rockets

2/9 of (boys that had rockets) had streamers

3/5=boys that had rockets

subsitue

2/9 of 3/5

'of' means multiply

2/9 times 3/5

remember that a/b times c/d = (ac) / (bd) so

2/9 times 3/5 = (2 times 3) / (9 times 5) = 6/45=2/15

so 2/15 of the boys had streamers

You multiply 3 and 2. Then multiply the 5 and 9. Use the 3 x 2 answer as the numerator then use the 5 x 9 answer as the denominator.