Math Unit 4 Review- Multi Digit Multiplication with Decimals

Math Unit 4 Review- Multi Digit Multiplication with Decimals

Multiplying Whole Numbers that end in Zero

• Multiply the non-zero digits first.

• Count the zeros in the factors (numbers we multiply).

• Add the zeros to the end of your product (multiplication answer).

Multiple Choice

500 x 30

• 15

• 150

• 1,500

• 15,000

Multiple Choice

6,000 x 8,000

• 14,000

• 140,000

• 480,000,000

• 48,000,000

Multiplying Whole Numbers- Place Value Sections Method

• Expand both numbers to show the value of each digit.

• Multiply the numbers on the top by each number on the left.

• Put it all back together and add up the products.

Multiple Choice

45 x 72

• 3,240

• 4,302

• 3,442

• 3,345

Multiple Choice

36 x 54

• 1,956

• 1,832

• 1,944

• 324

Multiplying Whole Numbers- Short Cut Method

• Multiply the digit in the ones place of the bottom number by everything above it. (Blue Highlighter)

• Don't forget the place holder or "magic" zero!!!

• Multiply the digit in the tens place by every digit above it, starting back in the ones place. (Green Highlighter)

• Add it up.

Multiple Choice

63 x 24

• 1,512

• 1,521

• 378

• 387

Multiple Choice

64 x 73

• 4,462

• 640

• 4,672

• 643

Multiplying by Powers of 10

• Powers of 10 are 10, 100, 1,000, 10,000, etc.

• Powers of 10 can also be: 10¹, 10², 10³, etc. The "flying number shows how many zeros are in that power. 10³ = 1,000

• When you multiply by powers of 10, count the zeros and shift the decimal point that many places to the right. If you have "gaps" fill them in with zeros.

Multiple Choice

36 x 10³

• 36

• 360

• 3,600

• 36,000

Multiple Choice

78 x 100

• 78

• 780

• 7,800

• 78,000

What if it's a decimal being multiplied by a power of 10??

• No worries! Just follow the steps.

• Count the zeros and shift the decimal that many places to the RIGHT.

• Fill in any gaps with a zero.

Multiple Choice

4.56 x 10²

• 4.56

• 45.6

• 456

• 4,560

Multiplying by 0.1, 0.01, 0.001

• Count how many digits are behind the decimal and shift the decimal to the LEFT that many places.

Multiple Choice

435 x 0.1

• 435

• 43.5

• 4.35

• 0.435

Multiple Choice

645 x 0.001

• 645

• 64.5

• 6.45

• 0.645

Multiplying Decimals

• Ignore the decimal.

• Multiply like normal.

• Count the digits behind the decimals in the problem.

• "Scoop" the decimal that many places to the LEFT in your answer.

Multiple Choice

5.6 x 3.8

• 21.28

• 2,128

• 2.128

• 34.62

Multiple Choice

3.7 x 62

• 29.6

• 229.4

• 22.94

• 2,960

Word Problems

• Underline or highlight what you know and what you want to know.

• Draw a picture if it will help you solve.

• There are only 4 operations in math; add, subtract, multiply, and divide. Decide which one will help you figure out what you want to know and solve. 

Multiple Choice

Ethan planted a tree that was 0.17 meters tall. The tree is now 10 times as tall as when he planted it. What is the height of the tree now?

• 17 meters

• 170 meters

• 1.7 meters

• 1,700 meters

Multiple Choice

Nevaeh earned 132 points when playing her video game. Vanessa earned four times as many points. How many points did Vanessa earn?

• 136 points

• 428 points

• 528 points

• 4,128 points

Multiple Choice

The sub shop customers use 13 boxes of ranch dressing each day. If each box of ranch dressing contains 25 packets of dressing, how many packets of dressing do the sub shop customers use each day?

• 3,255 packets

• 325 packets

• 91 packets

• 225 packets

Poll

I am prepared for my Unit 4 Math Test. I have completed all of the video lessons and assignments for Unit 4 and have practiced all of the new skills I have learned. (Hint: If you don't answer strongly agree or agree, you NEED TO DO THOSE THINGS FIRST!)

• strongly agree

• agree

• disagree

• strongly disagree