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Double Digit

Choose two digits and arrange them to make two double-digit numbers. Now add your double-digit numbers. Now add your single digit numbers. Divide your double-digit answer by your single-digit answer. Try lots of examples. What happens? Can you explain it?

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Number Detective

Follow the clues to find the mystery number.

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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?

Reach 100

Stage: 2 and 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Simply writing out the numbers $1 - 9$ along the top of your paper can be a great help.

Imagine arranging your four two-digit numbers in columns to do the addition sum, like this:

$5 \: 2$
$1 \; 9$
$5 \; 1$
$2 \; 9$

If the total has to be $100$, think about how the four digits you choose could add to make the $0$ in the units column, then look at the tens column.