Math questionaire

Mental strategies- 27.01.2013

Do it mentally or for practice. You may not do it in your notebook

Finding Compatibles (Review)

This strategy for addition involves looking for pairs of numbers that combine to make a sum that will be easy to work with. Some examples of common compatible numbers include 1 and 9; 40 and 60; 75 and 25 and 300 and 700.

Examples

a) For 3 + 8 + 7 + 6 + 2, think,“3 + 7 is 10, 8 + 2 is 10, so 10 + 10 + 6 is 26.”

b) For 25 + 47 + 75, think, “25 and 75 is 100, so 100 and 47 is 147.”

c) For 400 + 720 + 600, think, “400 and 600 is 1000, so the sum is 1720.”

d) For 3000 + 7000 + 2400, think, “3000 and 7000 is 10 000, so 10 000

and 2400 is 12 400.”

Practice Items

11 + 59 =                                         60 + 30 + 40 =

75 + 95 + 25 =                                 475 + 25 =

625 + 75 =                                       300 + 437 + 700 =

800 + 740 + 200 =                           900 + 100 + 485 =

400 + 1600 + 3000 =                       9000 + 3300 + 1000=

3250 + 3000 + 1750 =                     2200 + 2800 + 600 =

3000 + 300 + 700 + 2000 =             3400 + 5600 =

0.6 + 0.9 + 0.4 + 0.1 =                      0.2 + 0.4 + 0.8 +=

0.7 + 0.1 + 0.9 + 0.3 =                     0.25 + 0.50 + 0.75 =

0.4 + 0.5 + 0.6 + 0.2 + 0.5 =            0.45 + 0.63 =               

1. Find a word worth 0.60 when A=0.01, B=0.02, C=0.03, etc.

e.g., SMUG = 0.19 + 0.13 + 0.21 + 0.07 = $0.60

2. Look at the dessert portion of the menu below. Three friends, Chris, Ward, and Phillip have decided that they will each buy a dessert and share the cost evenly. What is the least that each will pay if each orders a different dessert? The most?

Peaches 'n' More  Desserts

Apple Pie            Rs. 1.89

Peach Cobbler    Rs. 2.04

Ice Cream           Rs.  0.84

Frozen Yogurt    Rs.0.96

Pecan Pie            Rs. 2.10

 3. What is 12/25 as a decimal?

0.5
0.48
0.4

4. To convert decimals to percentages multiply by 100.

a)      Write 0.35 as a percentage.

Similarly, 0.2 becomes 0.2 × 100% = 20%, and 0.375 becomes 0.375 × 100% = 37.5%.

Write the following decimals as percentages:

a) 0.34
b) 0.005

5. Convert to a decimal, then multiply by 100%

³/₈ = 3 ÷ 8 = 0.375

0.375 × 100% = 37.5%, so 3/8 = 37.5%

Write ⁵/₈ as a percentage

 6. To convert from percentages to decimals or fractions, divide by 100.Question

a) Write 67% as a decimal.
b) Write 5% as a fraction.

7. What is 12/25 as a decimal? 

8. What is the value of the expression below, when z = 1?

      8.75 − (3.625 − z )

a)   2.625

b)   4.125

c)   6.125

d)   6.135

9. Sammy is converting the number of acres of land his grandfather’s farm covers

to the number of square miles it covers. He will multiply the number of acres by

one thousand, five hundred sixty-two millionths. How is this number written in

standard form?

a)  0.001562

b)  0.01562

c)   1,000.000562

d) 1,562

10. Heavy rains caused the water level of a lake to rise eight hundred sixty-four thousandths of a meter. Which number is equivalent to eight hundred sixty-four thousandths?

a)   0.0864

b)   0.864

c)   86,400

d)  864,000

For 25.01.2013

Break Up and Bridge (Review)

This strategy is similar to front-end addition except that you begin with all of the first number and then add on parts of the second number beginning with the largest place value.  

Examples

a) For 45 + 36, think, “45 and 30 (from the 36) is 75, and 75 plus 6 (the

rest of the 36) is 81.”

b) For 537 + 208, think, “537 and 200 is 737, and 737 plus 8 is 745.”

c) For 5300 plus 2400, think, “5300 and 2000 (from the 2400) is 7300

and 7300 plus 400 (from the rest of 2400) is 7700.”

d) For 3.6 plus 5.3, think, “3.6 and 5 (from the 5.3) is 8.6 and 8.6 plus

0.3 (the rest of 5.3) is 8.9.”

Practice Items

37 + 42 =                   72 + 21 =                          88 + 16 =

74 + 42 =                   325 + 220 =                     301 + 435 =

747 + 150 =               142 + 202 =                     370 + 327 =

7700 + 1200 =           4100 + 3600 =                 5700 + 2200 =

7300 + 1400 =           2800 + 6100 =                 3300 + 3400 =

4.2 + 3.5 =                 6.3 + 1.6 =                       4.2 + 3.7 =

6.1 + 2.8 =                 0.32 + 0.56 =                   2.08 + 3.2 =

4.15 + 3.22 =             5.43 + 2.26 =                   6.03 + 2.45 =

15.45 + 1.25 =           43.30 + 7.49 =                 70.32 + 9.12 =

Mental Computation – Addition

Your goal for learning mental computation is to have a wide variety of mental methods, use opportunities where each method can be employed, and   use mental methods regularly to improve your skills.

• Front End Addition (Review)

This strategy involves adding the highest place values and then adding

the sums of the next place value(s).

  

Examples

a) For 37 + 26, think: “30 and 20 is 50 and 7 and 6 is 13; 50 plus 13 is 63.”

b) For 450 + 380, think, “400 and 300 is 700, 50 and 80 is 130; 700 plus

130 is 830.”

c) For 3300 + 2800, think, “3000 and 2000 is 5000, 300 and 800 is

1100; 500 plus 1100 is 6100.”

d) For 1.4 + 2.5, think, “One plus two is 3, and 4 tenths plus 5 tenths is

9 tenths, so the answer is 3 and 9 tenths. 3.9

Practice Items

45 + 38 =                 34 + 18 =                                  53 + 29 =

340 + 220 =             470 + 360 =                              607 + 304 =

3500 + 2300 =         5400 + 3 400 =                         6800 + 2100 =

4.6 + 3.2 =               5.4 + 3.7 =                                1.85 + 2.25 =

3.3 + 2.4 =                6.6 + 2.5 =                                0.36 + 0.43 =

Some sums on multiplication and division of Decimals

1.     Multiply    2.45   X   3.2                       2. Multiply  2.08  X 3.9

3.  Multiply   2.654  X  5.05                       4 Divide. 3.09 ÷  3.2

5. Divide     6.789  by 4.2