# math

A number consists of two digits whose sum is 9. if three times the number is equal to eight times the number formed by interchanging the digits. find the number

1. 👍 7
2. 👎 0
3. 👁 686
1. let the unit digit be x
and the tens digit be y
so x+y = 9 ---> y = 9-x

the number is 10y+x
the number reversed is 10x + y

3(10y+x) = 8(10x + y)
30y + 3x = 80x + 8y
22y = 77x
2y = 7x
2(9-x) = 7x
18 - 2x = 7x
18=9x
x=2
y=7

the number is 72

check:
number is 72
reverse is 27
is 3(72) = 8(27) ? , YES

1. 👍 9
2. 👎 0

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