PARTS OF NATURAL NUMBERS  2

PROBLEMS (2)

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21.   In each column, calculate half of each number mentally.

  21.  1  ½   10  5   100  50
  21.  2  1   20  10   200  100
  21.  3     30  15   300  150
  21.  4  2   40  20   400  200
  21.  5     50  25   500  250
  21.  6  3   60  30   600  300
  21.  7     70  35   700  350
  21.  8  4   80  40   800  400
  21.  9     90  45   900  450

22.   Calculate half mentally.

  22.  a)  11     b)  15     c)  17     d)  21  10½
 
  13  e)  23  11½   f)  29  14½   g)  33  16½   h)  57  28½
 
  13.  i)  28  14   j)  36  18   k)  52  26   l)  114  57
 
  13  m)  130  65   n)  350  175   o)  560  280   p)  770  385
 
  22  q)   7.90  3.95   r)   14.70  7.35   s)   15.30  7.65   t)   25.20  12.60

23  a)  Two and a half times $9.00 = $18.00 + $4.50 = $22.50

23.  b)  Three and a half times $7.00?  = $24.50

23.  c)  Four and a half times $11.00?  = $49.50

23.  d)  Six and a half times $5.00?  = $32.50

24.  How much is a fourth or a quarter of these?  (Take half of half.  What
24.  percent is this?  25% )

a)  64  16   b)  52  13   c)  56  14   d)  92  23
 
e)  $1.08  $.27   f)  $6.12  $1.53   g)  $10.32  $2.58   h)  $18.04  $4.51

25.  How much is 25% of these?

a)  $9  $2.25   b)  $14  $3.50
 
c)  $21  $5.25   d)  $50  $12.50
 
e)  $10.40  $2.60   f)  $60.20  $15.05
 
g)  $104.32  $26.08   h)  $216.28  $54.07  

26.  a)  How many seconds are there in a quarter of a minute?
10.  a)  (1 minute = 60 seconds) 15

26.  b)  How many seconds are in three quarters of a minute?  45

27.  Multiplying by 5.  Take half the multiplication by 10.

   17.  5 × 24 = 120   5 × 18 = 90   5 × 141 = 705
 
   27.  5 × $5.40 = $27   5 × $68.20  = $341   5 × $30.50 = $152.50

28.  How much is 5% of

a)  $44?  $2.20   b)  $18?  $.90
 
c)  $68?  $3.40   d)  $150?  $7.50
 
e)  $127?  $6.35   f)  $325?  $16.25

29.  You invest $4,000 in a fund that earns 5% interest each year.  If you
24.  leave the money in the fund and do not touch it, then at the end of
24.  two years, how much money will you have?

(Compare Problem 24, Lesson 4.)

$4,410.  For, at the end of the first year, you will have earned 5%, or $200, in interest, so that you now have $4,000 + $200 = $4,200.  At the end of the second year, 5% of that is $210. You now have $4,200 + $210 = $4,410.

30.  Multiplying by 15.

13.  a)  15 × 12 = 180  b)  15 × 16 = 240

18.  c)  15 × 24 = 360  d)  15 × 46 = 690

31.  How much is 15% of

19.  a)  $20?  $3  b)  $30? $4.50   c)  $18?  $2.70

19.  d)  $40? $6   e)  $60?  $9   f)  $70?  $10.50


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