Use known facts to multiply

Some people (especially those who still use feet and inches!!) think it is important to know how to multiply by 12. It?s easy ? just add 10 times the number to 2 times the number.

Using mental methods to multiply decimals by 10, 100 and 1000.

To multiply by 21, just multiply by 20 and then add the number on. (To multiply by 20, double and times by 10.)

Multiply by 10, 100 and 100 using place value charts

Multiplying large numbers by 100 and 1,000.

All these questions are about mentally multiplying by 100 and 1000, including decimals.

When multiplying 2-digit numbers by 1-digit in your head usually it is easier to start with the tens.

Multiplying three digit multiples of 100 is fairly easy, but there are some addition adjustments to make on some of these.