ratios and percentage question

Question

A certain concrete mixture contains 30% cement and 20% sand. How many pounds of this mixture and how many pounds of sand should be combined with 225 lb of cement to make a mixture that is 35% cement and 25% sand?

Answer 1

100-35=65

35-30= 5

65/5 =13

13(225)=2925 lbs of 30%

to get 3150 lbs of 35%

.3(2925)+225= 877.5+225= 1102.5 lbs concrete

.35(3150)=1102.5 concrete

.25(3150)=787.5 lbs sand

3150+787.5= 3937.5 35%/25%

mix 2925 lbs 30%,/20% 225 lbs concrete, and 787.5 lbs sand to get 3937.5 35%/25% concrete/sand

disclaimer

no guarantees this is error free

this is the type of problem

where you feel like saying to the

problem inventor: go pound sand