Six Is the Sum

What do the digits in the number fifteen add up to? How many other numbers have digits with the same total but no zeros?

(w)holy Numbers

A church hymn book contains 700 hymns. The numbers of the hymns are displayed by combining special small single-digit boards. What is the minimum number of small boards that is needed?

ABC

In the multiplication calculation, some of the digits have been replaced by letters and others by asterisks. Can you reconstruct the original multiplication?

Number Detective

Stage: 2 Challenge Level:

Lewis sent us his solution. He's explained each step very clearly.

Here are all the possible numbers:18, 86, 120, 42, 46, 64, 80, 8, 22, 83.

The number has two digits, so it can't be 120 or 8. So the possible numbers now are 18, 86, 42, 46, 64, 80, 22, 83.

Both of the digits are even, so the number can't be 18 or 83. So the possible numbers now are 86, 42, 46, 64, 80, 22.

The digit in the tens place is greater that the digit in the unit (or ones) place, so the number can't be 46 or 22. So the possible numbers now are 86, 42, 64, 80.

The units (or ones digit) is not in the three times table, so the number can't be 86. So the possible numbers now are 42, 64, 80.

The tens digit is not double the ones digit, so the number can't be 42. So it can only be 64 or 80.

The sum of the two digits is a multiple of five, so the number can't be 80, so it must be 64.