Question 159566
sand is 100%
Convert the percentages to decimal
100%=1
40%=.4
60%=.6

X=number of kilograms of sand

50(.4)+1(X)=(X+50)(.6)

The quantity hasn't changed only the percentage composition

Use the distributive property

20+X=.6X+30
Subtract .6 from both sides and subtract 20 from both sides

0.4X=10

X=25 kilograms of sand needed

Double check

50(.4)+25=75(.60)

45=45