Also: Using the table on page 824, if you have a 20 year mortgage for $80,000
at 7%,

a) what is your monthly payment? 80 × 7.75299 = 620.2392

b) what is the total of all your payments? 20 × 12 × 620.2392 =
148857.41

c) how much interest will you pay in total? 148857.41 - 80000 = 68857.41

d) what fraction of your total payments is interest? 68857.41/148857.41 = .4626

e) what fraction of your first payment is interest? (80000 ×
.07/12)/620.24 = .7524

p.239 - Also: Find all solutions to 2 + x = 3 (mod 5) We want 2+x = 3, 8, 13,
18, etc., hence x = 1, 6, 11, 16, etc. (including -4, -9, etc.)

Find all solutions to 2x = 3 (mod 5) We want 2x = 3, 8, 13, 18, etc., hence x =
1.5, 4, 6.5, 9, etc. (including -1, -3.5, -6, etc.)

If September 1 is a Tuesday, what day of the week is October 1? 1+(4 × 7)
= 29 so September 29 is a tuesday, two days later is a thursday. (or, the
number of days in September is 2 (mod 7), hence October 1 is two days later
than September 1)