96 P5.ST.JC.18121205
Level 3
The average cost of some books is $30.
If 3 of the books are now each $15 more,
the average cost of the books becomes $35.
How many books are there altogether?
3 m
2 averages Averaging out Average with unknown quantity Number x value Units equations Units table
97 P6.ST.JC.18121421
Level 3
Fill in the blanks.
Number of boys at first is 40% of the children.
Number of boys is then decreased to 30%.

  1. Number of boys at first = _____ u
  2. Number of boys in the end = _____ u
  3. Decrease in the number of boys = _____ u
  4. Number of children in the end = _____ u
4 m
Percent to units Percent change to Unchanged quantity Units table
98 P5.ST.JC.18121206
Level 3
The average cost of some books is $30.
If 3 of the books are now each $15 more and
2 of the books are now each $5 less,
the average cost of the books becomes $32.
How many books are there altogether?
3 m
2 averages Averaging out Average with unknown quantity Number x value Units equations Units table
99 P5.ST.JC.18121207
Level 3
The average cost of some books is $10.
After 2 new books are added,
it adds another $60 to the total cost.
As a result, the average cost of all the books increases to $20.
How many books are there at first?
3 m
2 averages Averaging out Average with unknown quantity Number x value Units equations Units table
100 P5.ST.JC.18121208
Level 3
The average cost of some books is $30.
After 2 new books are added,
it adds another $10 to the total cost.
As a result, the average cost of all the books decreases to $20.
How many books are there at first?
3 m
2 averages Averaging out Average with unknown quantity Number x value Units equations Units table

5 per page

10 per page

20 per page

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