Squaring Numbers
Multiplying Numbers
Dividing Numbers
 any by 0.125
 2 digits by 1 1/9
 2 digits by 1 1/8
 2 digits by 1 1/7
 2 digits by 1 1/6
 2 digits by 1 1/5
 2 digits by 1 1/4
 2 digits by 1 2/7
 2 digits by 1 1/3
 2 digits by 1 2/5
 2 digits by 1 3/7
 2 digits by 1 1/2
 2 digits by 1 3/5
 2 digits by 1 2/3
 2 digits by 1 3/4
 2 digits by 1 4/5
 2 digits by 2 2/9
 2 digits by 2 1/4
 2 digits by 2 1/3
 2,3 digits by 2 1/2
 2 digits by 2 2/3
 2 digits by 2 6/7
 2 digits by 3 1/8
 2,3 digits by 3 1/3
 2 digits by 3 1/2
 2 digits by 3 4/7
 2 digits by 4 1/6
 2 digits by 4 2/7
 2 digits by 4 4/9
 2 digits by 4 1/2
 2 digits by 5
 2 digits by 5 5/7
 2 digits by 6 1/4
 2 digits by 6 2/3
 2 digits by 7 1/7
 2 digits by 7 1/2
 2 digits by 8 1/3
 2 digits by 8 4/7
 2 digits by 12 1/2
 2 digits by 15
 2,3 digits by 16 2/3
 2,3 digits by 25
 2,3 digits by 33 1/3
 2,3 digits by 35
 2 digits by 37 1/2
 2 digits by 40
 2 digits by 45
 2 digits by 50
 2 digits by 62 1/2
 2 digits by 66 2/3
 2,3 digits by 75
 2 digits by 83 1/3
 2 digits by 87 1/2
 2 digits by 125
 2 digits by 166 2/3
 2 digits by 250
 2,3 digits by 333 1/3
 2 digits by 375
 2 digits by 625
 2 digits by 875
 3 digits rep./37+41
 6 digits rep. by 15873
 6 digits rep. by 7, then 13
 6 digits rep. by 13, then 11
 6 digits rep. by 7,11,13, subtract 101
 6 digits rep. by 37037 x 5
 mixed numbers by 2
 diff. of squares of 2 consec. 2digit numbers
 diff. of squares of 2 different 2digit numbers
 sqrt of squares of 2digit numbers ending in 1
 sqrt of perfect squares ending in 5
Adding Numbers
Subtracting Numbers
Finding Percents
Calculation
Practice Exercises
Full List

Dividing a 2 or 3digit number by 25
 Select a 2digit number. (Choose larger numbers when you feel sure about the
method.)
 Multiply by 4 (or by 2 twice).
 Move the decimal point two places to the left.
Example:
 The 2digit number chosen to divide by 25 is 38.
 Multiply by 4: 4 × 38 = 4 × 30 = 120 + 32 = 152.
 Move the decimal point 2 places to the left: 1.52
 So 38 divided by 25 = 1.52.
See the pattern?
 The 3digit number chosen to divide by 25 is 641.
 Multiply by 2 twice:
2 × 64 = 1282.
2 × 1282 = 2400 + 164 = 2564.
 Move the decimal point 2 places to the left: 25.64.
 So 641 divided by 25 = 25.64.
Practice multiplying left to right or by 2 twice and you will be able to do these
computations quickly and accurately.
