Fun algebra problem.

[notfred]

This isn't really too difficult if you keep everything organized.

Jimmy went shopping for a Fourth of July picnic. In the first store, he spent half of what he had plus $10 on meat for the barbecue. In the second, he spent half of what was left plus $2 for soda. In the third, he spent half of what was left plus $2 for paper plates. In the fourth, he spent four-sevenths of what was left for mustard and ketchup. He had $3 left. How much did he start with? It's on my calendar.

🙂

 

[Mnementh]

Originally posted by: notfred
This isn't really too difficult if you keep everything organized.

Jimmy went shopping for a Fourth of July picnic. In the first store, he spent half of what he had plus $10 on meat for the barbecue. In the second, he spent half of what was left plus $2 for soda. In the third, he spent half of what was left plus $2 for paper plates. In the fourth, he spent four-sevenths of what was left for mustard and ketchup. He had $3 left. How much did he start with? It's on my calendar.

🙂

$100

edited cause I automatically put £ instead of $

 

[MrChad]

x = amount he starts with

3 = (((0.5x - 10)0.5 - 2)0.5 - 2)*(3/7)
7 = ((0.5x - 10)0.5 - 2)0.5 - 2
18 = (0.5x - 10)0.5 - 2
40 = 0.5x - 10
x = $100

 

[Atomicus]

100

used logic, no calculations

 

[notfred]

Originally posted by: MrChad
x = amount he starts with

3 = (((0.5x - 10)0.5 - 2)0.5 - 2)*(3/7)
7 = ((0.5x - 10)0.5 - 2)0.5 - 2
18 = (0.5x - 10)0.5 - 2
40 = 0.5x - 10
x = $100

Wow, you certainly did that a lot easier way than I did. I came up with this and solved it:
x - (.5x+10) - (.5(x - (.5x+10))+2) - (.5(x - (.5x+10) - (.5(x - (.5x+10))+2))+2) - (4/7)(x - (.5x+10) - (.5(x - (.5x+10))+2) - (.5(x - (.5x+10) - (.5(x - (.5x+10))+2))+2)) = 3

 

[Mnementh]

Originally posted by: Atomicus
100

used logic, no calculations

me too, well except for the adding and multiplying heh...

 

[notfred]

Originally posted by: Atomicus
100

used logic, no calculations

How's that?

 

[sillymofo]

Wait... lemme run and get my 6 yrs old nephew. 😛

 

[Spikesoldier]

do it backwards, alot easier.

 

[Atomicus]

Originally posted by: Spikesoldier
do it backwards, alot easier.

Yea, basic logic. Times 7 then divide by three because its what you multiply the # before it to get the remaining $3 with. Now, I just work backwards mentally, adding cash before the multiplying because if you work backwards you have to follow the opposite of PEMDAS or something, OMFG

Mathematical logic is an intuitive skill in an engineer, especially one who needs to do the math right or else someone dies AKA me the civil/agro engineer :frown: