by John
(UK)
2-digit numbers
There are three boxes to be added together to get 87.
The first box is ten more than the second and the
second is ten more than the third.
_ + _ + _ = 87
Let x be the first number
Let y be the second number
Let z be the third number
Then, we get the following 3 equations
x + y + z = 87 (1)
x = y + 10 (2)
y = z + 10 (3)
Using (3), we get z = y - 10
Substitute y - 10 for z and y + 10 for x in (1)
y + 10 + y + y - 10 = 87
3y = 87
y = 29
z = y - 10 = 29 - 10 = 19
x = y + 10 = 29 + 10 = 39
Therefore, 39 + 29 + 19 = 87
Jul 20, 21 10:08 AM
Learn to calculate the mean of a discrete random variable with this easy to follow lesson