1. 2
   4
2. 8
   16

2+2=4. We thought we'd start you off with an easy one.

1. 5
   10
2. 50
   1,000

5x10=50. Multiplying by 10 is easy. Whenever you multiply a number by 10, just add a zero to the number.

1. 4.5
   300
2. 15
   2

15% of 30 is 4.5. When figuring 15%, just take 10%, which is 3, and add half of that, which is 1.5.

1. 210
   231
2. 111
   211

21x11=231. To multiply a number by 11 in your head, just multiply by 10 (or add a zero to the original number) and add one more of the original number. It looks like this: 21, plus a zero, is 210. Then add 21. The answer is 231.

1. 5
   25
2. 100
   15

5x5=25. Basic math tables, folks.

1. 1,600
   185
2. 1,800
   750

360x5=1,800. To multiply a number by 5, just divide it in half, then add a zero.

1. 999
   768
2. 898
   1,013

648+250=898. For this problem change the 648 to 650 to make it easier to do, then subtract 2 from the result.

1. 23.5
   2.35
2. .0235
   1.7

10% of 235 is 23.5. To find 10% of a number, just move the decimal point to the left one place.

1. 200
   2,000
2. 20,000
   2,100

200x100=20,000. To multiply two numbers with zeroes, just multiply the numbers, then add all the zeroes. It looks like this 2x1=2, then add four zeroes. The answer is 20,000.

1. 498
   311
2. 109
   231

1,000-689=311. To subtract a large number from 1,000, just round the number up to the closest 100, then subtract and add on the remainder. So, think of 100-689 as 1000-700, then add 11.

1. 5.63
   .563
2. 5,630
   563

563x10=5,630. To multiply a number by 10, just add a zero.

1. 1,250
   5,000
2. 500
   7,500

250x20=5,000. To multiply a number by 20, just double the number, then add a zero.

1. 12.50
   125
2. 12,500
   250

1,250 ÷ 10= 125. To divide a number that ends in zero by 10, just remove the zero.

1. 6
   12
2. 7
   9

3x4=12. We figured you'd welcome an easy one for a change.

1. 141
   242
2. 1063
   222

22x11=242. To multiply a number by 11, just multiply the number by 10, then add the number.

1. 18
   56
2. 81
   72

9x9=81. It's on the high side of the multiplication table, but you should still know this one by heart.

1. 4.50
   2,250
2. 950
   1,450

450x5=2,250. To multiply a number by 5, just divide the number in half, then add a zero.

1. 3,700
   470
2. 4,700
   970

4,200+500=4,700. To add thousands, just think of them as hundreds. So, 42 hundreds plus 5 hundreds, is 42+5, which is 47 hundreds, or 4,700.

1. 54
   230
2. 540
   360

200+300+40=540. Think of this as 2 hundreds plus 3 hundreds plus 40.

1. 78
   87
2. 51
   102

69+18=87. Think of this as 70+18=88, then subtract 1 to get 87.

1. 1,000
   1,100
2. 100
   110

10x10=100. Break time.

1. 5,600
   560
2. 56
   5,560

56x100=5,600. To multiply any number by 100, just add two zeroes to the number.

1. 3.69
   36.9
2. 3690
   3.069

369 ÷ 10=36.9. To divide any number by 10, just move the decimal to the left one place.

1. 240
   120
2. 480
   460

240x2=480. To multiply a number by two, just double it, or add it to itself.

1. 170
   100
2. 80
   150

70+20+80=170. Since we can easily see that 20+80=100, do that part of the problem first, then add 70 to get the answer of 170.

1. 96
   171
2. 138
   143

25+38+75=138. We can easily see that 25+75=100, so lets rearrange the problem so that it's easier.

1. 39.6
   3960
2. 3.96
   0.396

396÷100=3.96. To divide any number by 100, just move the decimal to the left two places.

1. 7
   8
2. 3
   9

15-7=8. It's easier to think of this as an addition problem. What do you need to add to 7 to reach 15?

1. 59
   82
2. 109
   111

53+56=109. Think of this as 50+50+3+6=109. It's about breaking numbers into easier to digest pieces.

1. 21.00
   210
2. 2,100
   2,700

7x300=2100. Just multiply 7x3, then add two zeroes.

1. 398
   294
2. 789
   463

6x49=294. Think of this as 6x50=300, then subtract 6 (because you're dealing with 49, not 50.)

1. 104
   53
2. 120
   115

8x15=120. Some numbers are easier to multiply in your head if you change them. For this one, cut one in half, then double the other to make it easier to manage. Half of 8 is 4, and double 15 is 30, so 4x30=120.

1. 7
   8
2. 9
   6

56 ÷ 8=7. Think of this as multiplication instead. What times 8 equals 56?

1. 0.56
   5.6
2. 560
   0.056

56÷100=0.56. To divide by 100, just move the decimal to the left two places. In this case, that makes the answer less than one.

1. 10
   100
2. 1000
   15

5+5=10. We made it easy-peasy for you. We figured your brain might be tired.