# What are the two digit multiple of 8 whose digit add up to 10?

64 is a two digit multiple of 8 (8x8) and if you add 6 and 4 together you get 10

# A three digit number whose digits add up to 9?

900, 810, 801, 720, 711, 702, 630, 621, 612, 603, 540, 531, 522, 513, 504, 450, 441, 432, 423, 414, 405, 360, 351, 342, 333, 324, 315, 306, 270, 261, 252, 243, 234, 225, 216, …207, 180, 171, 162, 153, 144, 135, 126, 117 and 108. NOTE : These numbers have digits whose sum is 9. An interesting mathematical fact is that they are also all divisible by 9. This applies to any number. If the sum of the digits = 9 or a multiple of 9 then the number is divisible by 9.

# Is there a two digitmultiple of 5 whose digits add up to 13?

the answer is 85

# Why do no digits of a prime number add up to 9?

Because they're in multiples of three - a quick way to tell if a number is a multiple of three is to add up the digits and see if the digits add up to a multiple of three e.g …576, 5+7+6=18, 1+8=9, 9 is a multiple of three

# What are all the two digit prime numbers neither of whose digits are prime?

11, 19, 41, 61, and 89

# What is largest two digit prime numbers whose digits are also prime?

73 satisfies your condition.

Answered

# What two digit prime number adds up to 5?

23 :]

Answered

# What is a two digit multiple of 5 whose digits add up to 13?

The number is 85.