Multiply by 10’s – Set 2

1. Multiply:
20  X 10 = ?

 
 
 
 

2. Multiply:
40  X 60 = ?

 
 
 
 

3. Multiply:
50  X 50 = ?

 
 
 
 

4. John tried to mutiply 80 X 90 by decomposing 80 and 90 into multiples of 10. His work is below:
80 X 90
= (8 X 10 ) + (9 X 10) Step 1
= (8 X 9) + (10 X 10) Step 2
= 72 + 100 Step 3
= 172 Step 4
FInd John’s mistake.

 
 
 
 

5. Joe tried to mutiply 90 X 30 by decomposing 90 and 30 into multiples of 10. His work is below:
90 X 30
= (9 X 10 ) X (3 X 10) Step 1
= (9 X 3) X (10 X 10) Step 2
= 12 X 100 Step 3
= 1200 Step 4
Find Joe’s mistake.

 
 
 
 

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