Number Sense Blog

Recall that 10% means 10 for each 100, 10 out of 100, or ten one-hundredths.   We can divide 1 by 10 to convert 10% to a decimal. 10% is equal to 0.1. Notice that dividing by ten moves the decimal point one place to the left.   To find...

“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...