The Answer is 36 btw.
3 + 6 = 9
3 x 6 = 2(3x6)
2(18) = 36
19
-109
1
Four. (100 x 10 = 1,000)
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.
19
It can have up to 5 digits.
Six.
81
You had me until "product." The product of 4 digits can't be prime.
362x(3x6)
-109
It can have one . . . 1.0 x 1.0 = 1 It can have two . . . 1.0 x 0.1 = 0.1 It can have three . . . 10 x 10 = 100 It can have four . . . 99 x 99 = 9801 and .01 x .01 = .0001
1
121
17 \
The number is 83.