Investigation 6024

Kamil saved up to buy a new phone case, which cost CZK 390. He only put ten and twenty crowns in the cash box. After two months of investigation, he had 25 coins in his treasury. When he calculated the total value of all the coins, he found out that he still needed more than 50 CZK for new packaging.

Correct answer:

a =  16
b =  9

Step-by-step explanation:


a+b = 25
10a+20b + 50 = 390

a+b = 25
10·a+20·b + 50 = 390

a+b = 25
10a+20b = 340

Pivot: Row 1 ↔ Row 2
10a+20b = 340
a+b = 25

Row 2 - 1/10 · Row 1 → Row 2
10a+20b = 340
-b = -9


b = -9/-1 = 9
a = 340-20b/10 = 340-20 · 9/10 = 16

a = 16
b = 9

Our linear equations calculator calculates it.



Did you find an error or inaccuracy? Feel free to write us. Thank you!







Tips for related online calculators
Do you have a linear equation or system of equations and looking for its solution? Or do you have a quadratic equation?

You need to know the following knowledge to solve this word math problem:

Related math problems and questions: