SOLUTION: How much of a cream base must be mixed with 20g of 0.5% dexamethasone and 75g of 0.025% of dexamethasone and 30g of 0.05% dexamethasone to make 0.02% of dexamethasone cream ? My

Question 805745: How much of a cream base must be mixed with 20g of 0.5% dexamethasone and 75g of 0.025% of dexamethasone and 30g of 0.05% dexamethasone to make 0.02% of dexamethasone cream ?
My own calculation : 20g x 0.5% = 0.1
75g x 0.25% = 0.1875
30g x 0.05% = 0.015
20g + 75g + 30g = 125
0.1 + 0.1875 + 0.015 = 0.3025/ 0.02% = 1512.5
1512.5 - 125 = 1387.5g
But the right answer 1375g Who solve it for me
Answer by josgarithmetic(39618) (Show Source): You can put this solution on YOUR website!
{Amount of pure dexamethasone}/{Amount of mixture}={Target concentration value of dexamethasone}

The cream base contains 0% dexamethasone, so adding the cream base affects the denominator but not the numerator.

LET w = grams of cream base to add to the other given quantities containing the dexamethasone.

Solve for w.
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