Number Sense Blog



Mathnasium #MathTricks: Divisibility (General Rule for 11s)

Nov 10, 2021

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.   To determine if the number 2,728 is divisible by 11, find the difference of the sum of alternating digit...



Mathnasium #MathTricks: Divisibility (3-digit Rule for 11s)

Nov 3, 2021

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.   To determine if the number 792 is divisible by 11, we find the sum of seven and two. Se...



Mathnasium #MathTricks: Divisibility (Rule for 3s)

Oct 29, 2021

A number is divisible by 3 if the sum of the digits is divisible by 3.   To determine if the number 87 is divisible by 3, we find the sum of its digits. Eight plus seven gives us a final sum of fifteen. Fifteen is divisible by 3. So,   ...



Mathnasium #MathTricks: Percents (Find 1%)

Oct 27, 2021

Recall that 1% means 1 for each 100, 1 out of 100, or one one-hundredth.   We can divide 1 by 100 to convert 1% to a decimal. 1% is equal to 0.01. Notice that dividing by one hundred moves the decimal point two places to the left.   To...



Mathnasium #MathTricks: Percents (Find 10%)

Oct 25, 2021

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...


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