1.In Rumpletick, 1/2 of 1% of the town's 100,000 families have incomes over 80,000 per year. How many families with incomes over 80,000 per year are in Rumpletick?
2.Suppose you know $x+2y=-1$ and $3y-x=-19$. What is $xy$?
1 - 1/2% means .50/100 =.005
.005 x 100,000 =500 number of families with income of over $80,000.
2 - Solve the following system:
{x+2 y = -1 | (equation 1)
3 y-x = -19 | (equation 2)
Add equation 1 to equation 2:
{x+2 y = -1 | (equation 1)
0 x+5 y = -20 | (equation 2)
Divide equation 2 by 5:
{x+2 y = -1 | (equation 1)
0 x+y = -4 | (equation 2)
Subtract 2 × (equation 2) from equation 1:
{x+0 y = 7 | (equation 1)
0 x+y = -4 | (equation 2)
Collect results:
Answer: | x = 7 and y = -4
