Problem number 26 of the rhind papyrus says: find a quantity such that when it is added to of itself the result is a 15. the modern day equation that models this problem is x + x = 15. what is the solution to the equation?
a) x = 10
b) x = 12
c) x = 15
d) x = 30

The correct answer is:

B) x = 12  

Explanation:

Problem number 26 states "Find a quantity such that when it is added to ¼ of itself the result is 15. "

Algebraically, this is represented as

x + ¼x = 15

Adding these together, we would have 1 ¼x = 15.

To write this as an improper fraction, we remember that 1 = 4/4; this gives us

4/4x + ¼x = 15

5/4x = 15

Divide both sides by 5/4:

(5/4x)÷(5/4) = 15÷(5/4)

x = 15÷5/4 = (15/1)÷(5/4)

To divide fractions, we flip the second one and multiply:

x = (15/1)×(4/5)

Multiplying fractions means we multiply the numerators and multiply the denominators:

x = (15×4)/(1×5) = 60/5 = 12

answer: -8.2562234e+13