The average cost of 3 textbooks is $30.
After another textbook that costs $90 is added,
- What is new total cost of all the textbooks?
- What is new average cost of all the textbooks?
(a)
Total cost of 3 textbooks
= 3 x 30
= $90
New total cost of all the textbooks
= 90 + 90
= $180
(b)
New total number of textbooks
= 3 + 1
= 4
New average cost of all the textbooks
= 180 ÷ 4
= $45
Answer(s): (a) $180; (b) $45