Question

若將一個兩位數(shù)的十位數(shù)字與個位數(shù)字對調(diào)后所得的新兩位數(shù)是其數(shù)字和的3倍，則原兩位數(shù)是     ；

Answer 1

72

解析解：設(shè)原數(shù)十位數(shù)為x 個位數(shù)為y,
則新數(shù)為10y+x
10y+x=3(y+x)
10y+x=3x+3y
7y=2x
x=3.5y
x和y都是1位數(shù),只有當(dāng)y=2的時候才成立
所以 y="2" x=7
原數(shù)為72