Here goes: 4 X 2 X 3 X 1 = 24
two
22
You had me until "product." The product of 4 digits can't be prime.
2
When using significant digits, the product has only the number of significant digits as the lowest number in the factors. "20" has two significant digits and "310" has three. Therefore, the product has to have two significant digits. 310 × 20 = 6200 6200 already has two significant digits.
Mutilply the values of the digits.
88
two
52 is a number whose digits have a product of 10.
22
You had me until "product." The product of 4 digits can't be prime.
2
If you mean, "What is the largest number of digits possible in the product of two 2-digit numbers" then 99 * 99 = 9801, or 4 digits. Anything down to 59 * 17 = 1003 will have 4 digits.
When using significant digits, the product has only the number of significant digits as the lowest number in the factors. "20" has two significant digits and "310" has three. Therefore, the product has to have two significant digits. 310 × 20 = 6200 6200 already has two significant digits.
400 x 4 = 1600 Therefore, four digits.
from 3 digits (10x10) to 4 digits (99X99)
The 2-digit number must be 20, because it is the only 2-digit number whose sum of its two even digits, 2 + 0 = 2, is greater than the product of its two even digits, 2 x 0 = 0. Moreover, 20 is a product of the two consecutive integers 4 and 5.