Powers of 10

1
Powers of 10
Subtract 1 from the power
Add 1 to the power
104 103 102 10



100
10-1
10-2
1
10
1
0.1
100
0.01
10000
1000
Multiply by 10
Divide by 10
2
TRUE OR FALSE?
Multiplication always makes numbers bigger
Division always makes numbers smaller
3
Calculator Challenge 1

• In your envelopes you will find
• A starting number
• A target number
• In pairs, take it in turns to multiply your
  starting number by any number you choose

Can you make your target number by only
multiplying?
Closest to the target number wins.
4
Try multiplying and dividing the numbers on the
left hand side by those on the right hand side.
Investigate
0.6 25
0.23
62.5
0.00482 800
0.09 1.5
0.1 1/100
0.01
10

100 1/10
x

5
Organise your findings into a table
Multiply Multiply Multiply Multiply Multiply Multiply Divide Divide Divide Divide Divide Divide
0.1 1/10 10 0.01 1/100 100 0.1 1/10 10 0.01 1/100 100
x
y
6
Multiply Multiply Multiply Multiply Multiply Multiply Divide Divide Divide Divide Divide Divide
0.1 1/10 10 0.01 1/100 100 0.1 1/10 10 0.01 1/100 100
0.00482
0.09
0.23
0.6
1.5
25
62.5
800
What can you see?
7
Calculator Challenge 2

• In pairs, choose a starting number between 1 and
  20.
• Choose a target number between 100 and 200.
• Take it in turns to divide your starting number.

Can you make your target number by only dividing?
Closest to target number wins.
8
What did you find?
Dividing by a number less than 1 makes things
bigger
9
Is the same as
Is the same as
Multiplying by Multiplying by Dividing by
0.1
0.01
Is the same as
Is the same as
Dividing by Dividing by Multiplying by
0.1
0.01
10
Multiplying and dividing by powers of 10

• 7.34 x 100

734
37.4 / 10
3.74
9.3 x 0.1
9.3 / 10
0.93
0.27 / 0.1
0.27 x 10
2.7
0.63 x 0.01
0.63 / 100
0.0063
5.96 / 0.01
5.96 x 100
596
11
What did you find out?
Multiplying by a number less than 1 makes things
smaller.
Dividing by a number less than 1 makes things
bigger