PARTS OF NATURAL NUMBERS  2

PROBLEMS (2)

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

  17.  1  ½   10  5   100  50
  17.  2  1   20  10   200  100
  17.  3  1½   30  15   300  150
  17.  4  2   40  20   400  200
  17.  5  2½   50  25   500  250
  17.  6  3   60  30   600  300
  17.  7  3½   70  35   700  350
  17.  8  4   80  40   800  400
  17.  9  4½   90  45   900  450

18.   Calculate half mentally.

  13.  a)  11  5½   b)  15  7½   c)  17  8½   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
 
  13  q)   7.90  3.95   r)   14.70  7.35   s)   15.30  7.65   t)   25.20  12.60

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

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

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

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

20.  How much is a fourth or a quarter of these?  (Take half of half.  What
15.  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

21.  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  

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

   17.  5 × 24 = 120   5 × 18 = 90   5 × 141 = 705
 
   17.5 × $5.40 = $27   5 × $68.20  = $341   5 × $30.50 = $152.50

23.  Multiplying by 15.

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

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

24.  How much is 15% of these?

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

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

Increase or decrease by a part

25  A photograph measures 9 inches by 12 inches.  If it will be enlarged
25.  by a third, what are the new dimensions?

12 inches by 16 inches

26.  In 1990, the population was 30,000.  By the year 2000, the population
26  had increased by a fifth.  What was the population in 2000?

36,000

27.  Last week a blouse cost $35.  This week the price was reduced by a
27.  tenth.   What is the price this week?   $31.50

28.  Janet used to earn $28,000 a year.  In her new job, she makes one
28.  quarter more.  How much does she make in her new job?  $35,000


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