## anonymous one year ago Please help! I don't understand this brian is an agriculture scientist who is testing different applications of insecticides on tomato plants. For part of the trial he is running now he needs 125 gallons of 12% solution of test chemical AX-14. Brain received only containers with 7% solution and 15% concentrations of test chemical AX-14. How much of each chemical should brian mix to run his trial?

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1. misty1212

HI!!

2. anonymous

HI!

3. misty1212

don't you hate word problems?

4. misty1212

we can still do it though, it is not that hard

5. anonymous

haha yes very much!

6. misty1212

we need a variable lets call the number of gallons of 15% solution $$x$$ then since the total number of gallons of solution is 125, the amount of 7% solution is $$125-x$$ so far so good?

7. misty1212

this is where you say "yes i get it so far" or "no where did the $$125-x$$ come from?"

8. anonymous

okay i get it

9. misty1212

ok the 15% part with $$x$$ gallons gives $0.15x$ solution and the remaining $$125-x$$ gives $0.07(125-x)$ and the total you want to be $$0.12\times 125$$ solution

10. misty1212

we can do this by solving $0.15x+0.07(125-x)=0.12\times 125$ or get rid of the annoying decimal points and solve $15x+7(125-x)=12\times 125$

11. misty1212

now it is a more or less routine linear equation to solve

12. anonymous

okay so 15x+875-7x=12 x 125

13. misty1212

yea now combine like terms etc

14. anonymous

8x+875=12 x 125 -4x + 875=125 -4x=-750 x=187.5

15. misty1212

i think there is a mistake somewhere here

16. misty1212

the 12 got dropped somewheres

17. misty1212

$8x+875=1500$

18. misty1212

$8x=625$

19. anonymous

oh yes i did somehow. it would be.. x=78.125

20. misty1212

that is what i get too

21. anonymous

okay thank you