Answer:
22.5 g
Explanation:
Let
x = mass of the 10% (0.1) cream
y = mass of the 2% (0.02) cream
We mix x grams of the 10% cream with y grams of the 2% cream to obtain 60 grams of a 5% (0.05) cream.
0.1 x + 0.02 y = 0.05 × 60
0.1 x + 0.02 y = 3 [1]
The sum of x grams and y grams is 60 grams.
x + y = 60
y = 60 - x [2]
We replace [2] in [1]
0.1 x + 0.02 (60 - x) = 3
0.1 x + 1.2 - 0.02 x = 3
0.08 x = 1.8
x = 22.5 g
I think there is a typo in the option A, because the correct answer is that you need 22.5 g of the 10% cream.
Yo can get the mass of the 2% cream by replacing this value in [2].
y = 60 - x = 60 - 22.5 = 37.5
