1 and the four-digit 7a4b are multiples of 18. If the number of four digits is as small as possible, what are the numbers A and B?

18=3*3*2

That is, b is an even number.

It is also known that it can be divisible by 9, and 7+4+a+b is a multiple of 9 (this is the same as 3).

So a+b = 7.

B is an even number. To minimize this number, a is the smallest.

Therefore, a = 1 and b=6.

The number is: 7 146.

2. A cuboid, the sum of its front and upper areas is 9 1 cm2. If its length, width and height are prime numbers, how many cubic centimeters is the volume of a cuboid?

Because 9 1=7* 13,

So we can divide 13 or 7 into two prime numbers.

If decomposition 7

Then its length, width and height are 5 213, and its volume is 5*2* 13= 130 cubic centimeter.

If 13 is decomposed,

Then its length, width and height are112 7, and its volume is11* 2 * 7 =154 cubic centimeters.