Number Sense Blog

Here is a number sense trick to subtract without borrowing.

To test if a number is divisible by 11, follow the general rule: the difference of the sum of alternating digits can be divided by 11.

One way to test if a three-digit number is divisible by 11 is to follow the 3-digit rule: the sum of the first and last digits equals the middle digit.

A number is divisible by 3 if the sum of the digits is divisible by 3.

Recall that 1% means 1 for each 100, 1 out of 100, or one one-hundredth.

Recall that 10% means 10 for each 100, 10 out of 100, or ten one-hundredths.

“Special percents” are easy to compute because they represent easy-to-calculate amounts.