Number Sense Blog

“Special percents” are easy to compute because they represent easy-to-calculate amounts.   0% means “none of it” 25% means “a quarter of it” 50% means “half of it” 100% means “all of it” 200% means “all of it, twice”   To f...

Here is a number sense trick to help you calculate multiplication using mental math.   We want to find the product of 5 x 4 x 3 x 2 x 1. Using our number sense, we want to find numbers close to ten or multiples of ten to make the multiplicat...

Here is a number sense trick to help you calculate subtraction using mental math.   We want to find the difference of 100 – 76. Using our number sense, we turn to “friendly numbers” to calculate how far apart are 76 and 100.   Starting...

Here is a number sense trick to help you calculate addition using mental math.   We want to find the sum of 9 + 8 + 7. Using our number sense, we turn to “friendly numbers” such as 10 or multiples of 10, to help make this math easier to work...

The word quarter means “4 parts the same,” “four equal parts”.   To find a quarter of any amount, cut the whole into “4 parts the same” and take any one part. The trick to doing this easily is to “cut it in half and then cut the half in half...