Matt's class spent 5/6 of an hour in science class. They dissected frogs for 3/4 of the time. What fraction of an hour did Matt's class dissect frogs?

Question

Matt's class spent 5/6 of an hour in science class. They dissected frogs for 3/4 of the time. What fraction of an hour did Matt's class dissect frogs?

Answer 1

1 hour = 60 minutes

1/6 hour = 60/6 = 10 mins

5/6 hour = 5 x 10 = 50 mins

Matt spent 50 mins in science class

Of that 50 mins, Matt spent 3/4 of the time dissecting

3/4 of 50 . . . I think of it as 3/4 X 50/1 = 150/4 = 37.5 mins spent dissecting

You might prefer .75 X 50 (same answer . . . 37.5)

What fraction of an hour is 37.5?

(Think first: it must be more than 1/2 or 30 mins but less than 3/4 or 45 mins---it's good to get "in the ballpark" before going too far)

Divide 37.5 by 60 to find the decimal form of the fraction you want = 0.625

I know this decimal from years of practice as 5/8 so 5/8 hr is the answer (I suppose you could give the answer as the fraction 625/1000 hr but most teachers want fractions simplified; or perhaps this is on a multiple choice test of some kind, in which case, the answer 625/1000 probably isn't a choice)