Maths fraction solving

Question

Mary had some beads. 3/5 of her beads were yellow. 5/7 of the remaining beads were red. The rest of the beads were black.

 

a) What fraction of the beads were black?

b) If she had 12 black beads, how many beads did she have altogether?

Answer 1

Umi, this is a tricky one for sure.

 

If 3/5 are yellow, then 2/5 must not be yellow, right? Again, if 5/7 of those are red, 2/7 are black.

 

(2/5)(2/7) = 4/35 are black

 

If 4/25 of the total is 12...

 

(4/25)t = 12

(25/4)(4/25)t = 12(25/4)

t = 75 beads total

 

Hope this helps!