Question 139780
 The first store he enters sells his favorite size nails at 9 cents per pound. At this price, the carpenter realized that he would be short $7.15 if he tried to buy the nails. The carpenter goes to a competing hardware store and finds that the nails sell for 6 cents a pound. He realizes that after paying for the nails, he would have $2.45 left over. How many pounds of nails is he trying to buy?
:
Let x = lb of nails required
Let y = amt of money he has
:
Write an equation for each store:
.09x = y + 7.15
.06x = y - 2.45
We can also write it, subtract and eliminate y:
.09x - y =  7.15
.06x - y = -2.45
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.03x = +9.60
x = {{{9.6/.03}}}
x = 320 lb of nails
:
check solution by finding the cost of each; the dif should be 7.15 + 2.45 = 9.60
320*.09 = 28.80
320*.06 = 19.20
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differs by 9.60