Lesson 13

Problems about comparing Elapsed-time problems

Notes Mental Math

Links

HomeworkProficiency

Activity

Practice

Mental Math Count up and down by 3’s between 3 and

36. 4 x 75 279 + 350 250 - 199 $15 + $7.75 Double $1.50 800/40 4 x 12, ÷ 6, x 8, - 4, ÷ 6, x 3, ÷ 2

Some Math Stories Are about Compare the Size of Two Groups

Subtraction pattern Larger – smaller = difference L – S = D

Example: There were 324 girls and 289 boys in the school. How many fewer boys than girls were there in the school?

Use the 4-step process to solve the problemStep 1: subtraction patternStep 2: larger – smaller = difference 324 – 289 = DStep 3: 324 girls – 289 boys = 35 sure boysStep 4: There were 35 fewer boys and girls in the school.

Elapsed-timeElapsed time is the length of time between two events

Elapsed time problems are like comparison problems. They have a subtraction patterns.

Later – earlier = difference L – E = D

Example: How many years were there from 1492 to 1620?

Step 1: Elapsed time problem (subtraction pattern)

Step 2: 1620 – 1492 = D

Step 3: 1620

- 1492

128 years

Step 4: There were 128 years from 1492 to 1620.

http://www.math.com/school/subject1/lessons/S1U4L6GL.html

http://www.kidsmath.com/e_int.html

A

1 ½ + ¾ = 2 ¼

20 ¼ - 2 ¼ = 18 inches

A

1 ½ + ¾ = 2 ¼

20 ¼ - 2 ¼ = 18 inches

Activity

Tom followed the directions on the treasure map. Started at the big trees, he walked five steps north. Then he turned right and walked seven steps. He turned right again and walked nine steps. Then he turned left and walked three steps. Finally, he turned left and walked 4 steps. In what direction was he facing? How many steps was he from the big tree?

Lesson 13

Practice A-bComplete #’s 1-29

What is the perimeter of a square which 1 side is 25 mm?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24

25 m

m

50 m

m

75 m

m

100

mm

None

of the

above

6% 6%0%

88%

0%

1. 25 mm

2. 50 mm

3. 75 mm

4. 100 mm

5. None of the above

8 / 4 x 2 8 / (4 x 2)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24

< > =

None

of the

above

11%6%

44%39%

1. <

2. >

3. =

4. None of the above

What is the next term in this sequence? 16, 24, 32, ___

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24

38 40 64 96

None

of the

above

6%

83%

11%

0%0%

1. 38

2. 40

3. 64

4. 96

5. None of the above

What is the place value of the 1 in 12,453,000,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24

Ten tr

illio

n

Trillio

n

Ten b

illio

n

Billio

n

Ten th

ousan

d

26% 26%

5%

0%

42%1. Ten trillion

2. Trillion

3. Ten billion

4. Billion

5. Ten thousand

What is the difference between the product of 6 and 4 and the sum of 6 and 4?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24

8 12 14 24

None

of the

above

0%

11% 11%11%

67%1. 8

2. 12

3. 14

4. 24

5. None of the above