
Source: Keming Primary
Source: Keming Primary
Unit cost
Plushie [u][u]
Keychain [u]
4u + 8(2u) = 20u Remainder money= (3/4) Buy more plushies with ( 1/2) (3/4) = (3/8)
1/4 money spent –> 20u
3/8 money spent –> (20u x 4) x (3/8) = 30u
1 plushie -> 2u => 30u/2u = 15 plushies
15+8 = 23
Hence Mr Robins bought 23 plushies altogether.
Here is a block diagram solution:
Explanation
A: 1 plushie (blue) can buy to 2 keychain (yellow).
So we see that 1/4 of his money can buy 10 plushies.
B: The remaining of his money can buy 3 x 10 = 30 plushies.
C: So half of the remaining money can buy 30/2 = 15 plushies.
Answer: He bought 8 + 15 = 23 plushies.
If each keychain costs L, each plushie costs 2L
Then ¼ of money can buy 4L+8*2L= 20L
Half of the remaining money = ½*(1-1/4)=3/8 which is 3/2*1/4 or you can understand it as 1.5 times what ¼ of money can buy.
So Half of the remaining money can buy 1.5*20L=30L and can buy 15 more plushies.
So in total Mr Robin bought 15+8=23 plushies altogether.