MENTAL ARITHMETIC: MULTIPLICATION

PROBLEMS (3)

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19.	Rounding off
	a)	Calculate in writing by distributing 2 to this difference:
		3 × (600 − 2) = 1800 − 6 = 1794
	b)	Multiply mentally:  3 × 598 = 1794

20.   Multiply each column mentally.  Treat problems with decimal points
20.   as dollars and cents.

6 × 99 = 594		2 × 2.95 = 5.90		7 × 11.98 = 83.86
5 × 79 = 395		3 × 4.95 = 14.85		5 × 16.96 = 84.80
3 × 89 =  267		6 × 5.98 = 35.88		7 × 24.98 =  174.86
8 × 39 =  312		5 × 7.99 =  39.95		3 × 19.95 =  59.85

Can you do these mentally, or with the least amount of writing?

21  At a political fund raising, fifty people paid $10,000 each to have
21. dinner with the President.  How much money was raised?  $500,000

22.  If your car gets 25 miles per gallon, how far could you go on 12
22 . gallons?  12 × 25 = 250 + 50 = 300 miles.

23.  What is the price of 4 airline tickets at $182 each?   $728

24.  What is the price of 6 airline tickets at $56.98 each?  $341.88

24.  What is the price of 60 tickets?  $3,418.80

25  If coffee sells for $3.95 a pound, what is the price of 4 pounds?
25.   $15.80

24.  What is the price of 40 pounds?  $158

26.  a)  How many days are there in 10 years?  Approximately 3,650.

26.  b)  How many days are there in 2 years?

26.   b) 2 × 365 = 600 + 120 + 10 = 730

26.  c)  How many days are there in 12 years?  3,650 + 730 = 4,380

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