Level 3
The average cost of some books is $75. When another 3 books are added, the total cost increases by $190. The average cost becomes $70. How many books are there in the end?
Level 3
The average cost of some books is $30.
When a book that costs $90 is added,
the average cost of the books becomes $40.
How many books are there in the end?
Level 3
The average cost of some books is $30.
When a book that costs $90 is removed,
the average cost of the books becomes $10.
How many books are there in the end?
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?
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?