Question

Solve this problem on paper using all four steps.

A girl scout troop sold cookies. If the girls sold 5 more boxes the second week than they did the first, and if they doubled the sales of the second week for the third week to sell a total of 431 boxes of cookies, how many did they sell each week?





So I'm supposed to figure this out using a single variable. Since the only week that isn't based on another week number is week one. I'm using it as X (variable). So week 1 is x, week 2 is x + 5, and week three is 2x + 5. So if I'm correct the equation to solve it should be x + x + 5 + 2x + 5 = 431. After simplifying it comes to 4x + 10 + 431. Then you subtract 10 from both sides and multiply both sides by the reciprocal of 4 to get the let side to only have x. which I subtract the 10 and get 4x = 421. After multiplying by the reciprocal of 4 (1/4?) however. I get a decimal. And I'm pretty sure you can't sell a quarter of a box of cookies.

Please tell me what I'm doing wrong?

Answer 1

Answer:they sold

1st week: 104

2nd week: 109

3rd week: 218

Answer 2

your mistake is that week 3 is twice of week 2
week2=x+5, twice of that is 2(x+5)=2x+10, you did not distribute the 2 to the 5 and you got 2x+5, that is your mistake


x is first week
2nd week is y
3rd is z

5 more the 2nd week than 1st week
x+5=y

3rd week is double 2nd wee
z=2y

total is 431

x+y+z=431
sub
y=5+x and z=2y
x+5+x+2y=431
sub 5+x for y
x+5+x+2(5+x)=431
x+5+x+10+2x=431
4x+15=431
minus 15
4x=416
divide by 4
x=104
add 4
x+5=109
double
2*109=218

they sold
1st week: 104
2nd week: 109
3rd week: 218