Being resilient

How many pairs of numbers can you find that add up to a multiple of 11? Do you notice anything interesting about your results?

Each clue in this Sudoku is the product of the two numbers in adjacent cells.

A country has decided to have just two different coins. Which totals can be made? Is there a largest total that cannot be made? How do you know?

How many ways can you find to put in operation signs (+, −, ×, ÷) to make 100?

Can you find six numbers to go in the daisy from which you can make all the numbers from 1 to a number bigger than 25?

By selecting digits for an addition grid, what targets can you make?

What happens when you add a three digit number to its reverse?

Can you find sets of numbers which satisfy each of our mean, median, mode and range conditions?

Take any four digit number. Move the first digit to the end and move the rest along. Now add your two numbers. Did you get a multiple of 11?

Charlie and Abi put a counter on 42. They wondered if they could visit all the other numbers on their 1-100 board, moving the counter using just these two operations: ×2 and -5. What do you think?