6th grade math percentage question

Question

I spend 15% of my money on food. I spend 15% of the remaining money on drinks. I have $50 left. How much money did I start out with?

Answer 1

Lets assume you have $100 at the start.

 

Spent 15% on food.

 

$100 * 15% = 100 * 15/100 = $15 spent on food.

 

The remaining money = $100 - $15 = $85

 

Spent 15% of remaining money on drinks.

 

$85 * 15% = 85 * 15 / 100 = $12.75

 

The remaining money = $85 - $12.75 = $72.25

 

When you started out with $100, you have $72.25 left, how much you started out with when you have $50 left? It is just a ratio problem now.

 

Started out money / $50 = $100 / $72.25

 

Started out money = 100 * 50 / 72.25 = $69.20

 

To check if the answer is correct, reverse the calculations.

 

You started out with $69.20.

 

15% spent on food

 

$69.20 * 15% = 69.20 * 15 / 100 = $10.38

 

Remaining amount = $69.20 - $10.38 = $58.82

 

15% spent on drink

 

$58.82 * 15% = 58.82 * 15 / 100 = $8.82

 

Remaining amount = $58.82 - $8.82 = $50

 

Thus $69.20 as answer for starting money is correct.

Answer 2

Nice work, Anil. I solved it the exact same way.  :-)