How many grams of 0.5% hydrocortisone cream must be mixed with 180 g of 2.5 % cream to make a 1 % w/w hydrocortisone cream? hint: use alligation method.

We need 540 grams of 0.5% hydrocortisone cream

Step-by-step explanation:

Lets call x the amount of grams needed. This means that the combined cream will have 180+x grams. We want x such that

x * 0.005 + 180*0.025 = (180+x)*0.01

Hence

0.005x + 4.5 = 1,8+0.01x

Lets put the x in the same side and take common factor

4.5-1.8 = 0.01x-0.005x

2.7 = (0.01-0.005)x = 0.005x

As a result

x = 2.7*0.005 = 540

We need 540 grams.

x= -3

step-by-step explanation:

step 1: simplify brackets

4 - x - 1 = 6

step 2: simpilfy

3 - x = 6

step 3: subtract 3 from both sides

-x = 6 - 3

step 4: simpilfy 6 - 3

-x = 3

step 5: multiply both sides by -1

x = -3