Category 15 Example 1 Question 1 - no calculation required
Total annual cost = annual membership + cost of p classes in a year = 25 + 20p
Category 15 Example 1 Question 2 - mental math
Cost of 5 classes is 20 x 5 = 100. Hence, total annual cost = 25 + 100 = 125
Category 15 Example 2 - mental math
Total books = existing books + 4 books per week for 7 weeks = 38 + 28 = 66
Category 16 Example 1 - no calculation required
Total earnings = h hours at $15 per hour + c cakes at $2.50 each = 15h + 2.5c
Category 17 Example 1 - no calculation required
The given equation can be interpreted as
total population in t years after 1998 = starting population in 1998 + average increase in population per year after 1998 for t years.
Hence, 130 is the average increase in population per year after 1998 for t years.
Category 17 Example 2 Question 1 - no calculation required
The given equation can be interpreted as
tusk size in m months after one year of birth = tusk size at one year + average increase in tusk size per month after one year of birth for m months.
Category 17 Example 2 Question 2 - no calculation required
For tusk size to increase by 1, 0.5583m must be equal to 1. Hence, m is the reciprocal of 0.5583 = 1/0.5583.
Category 18 Example 1 - no calculation required
Total bushes = x + y = 12
Total cost = cost of x bushes at $35 each + cost of y bushes at $55 each --> 520 = 35x + 55 y