Welcome to Mathnasium’s Math Tricks series. Students are often taught that division is the opposite of multiplication, and therefore should rely on their multiplication facts to divide; this can be difficult when the number to divide by (the divisor) extends beyond these facts. Today we are using number sense to divide, when the divisor is a power of two. The trick is to cut the original number (the dividend) in half the appropriate number of times (the “power” amount).

Divide by the power of two using this Mathnasium Math Trick in the problem below.

Example: 224 ÷ 32.

   Step 1: Identify the divisor.

Thirty-two is a power of two: 32 = 25 = 2 × 2 × 2 × 2 × 2

   Step 2: Cut the dividend in half the “power” amount.

Since 32 is equal to 2 to the power of 5, we cut in half 5 times:

224 cut in half is 112

112 cut in half is 56

56 cut in half is 28

28 cut in half is 14

14 cut in half is 7

   Answer: 7

Now you are ready to divide by powers of two. Click here for more practice problems, then check your answers here.

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