P5 Math: Blue and Green Stickers

Blue stickers were sold in packets of 15 each. Green stickers were sold in packets of 40 each. Rachel bought 5 packets of blue stickers and some packets of green stickers. Farah bought 13 packets of blue stickers and some packets of green stickers. Both girls bought the same total number of packets of stickers.

a) How many more green stickers did Rachel buy than Farah ?

b) After Rachel used 3/5 of her green stickers and Farah used half of her green stickers, they both had 452 green stickers left altogether. How many blue and green stickers did Farah buy altogether?

Solution:

Notes that total number of packets of stickers are same for both girls
or
Total for Rachel (tR) = bR + gR
Total for Farah (tF) = bF + gF
So, tR = tF

a) 

tR = tF
bR + gR = bF + gF
5 + gR = 13 + gF
gR = 8 + gF, or gR - gF = 8
means Rachel bought 8 green packets more than Farah.
Since each green packet consists of 40 stickers, it means Rachel had 8 x 40 = 320 green stickers more.

b) Left green stickers = 2/5 from Rachel + 1/2 from Farah

2/5*gR + 1/2*gF = 2/5*(8 + gF) + 1/2*gF = 16/5 + 9/10*gF (1)

Here we must convert the unit of green stickers to packet of green stickers:
452 green stickers are packed in 452 / 40 packets = 113 / 10 packets (2)

Join (1) and (2):
16/5 + 9/10*gF = 113/10, gF = 9

So Farah had 9 green packets.
Total Farah had 13 blue packets + 9 green packets = (13*15) + (9*40) = 555 stickers