Question

The scatter plot shows the number of stamps Katie collected in different months:. . Plot ordered pairs 1, 30 and 2, 70 and 3, 110 and 4, 150 and 5, 190. . What is the approximate predicted number of stamps she collected in the 25th month?. . A. 980. B.990. C.1000. D.1010

Answer 1

B.) 990

Explanation:

Here's another way of looking at it.

Make an equation representing the graph.

y = mx + b

to find m (slope) I used points (1,30) and (4,150) to get 40 as the slope.

y = 40x + b

to solve for b (y-intercept) I plugged in any point that I wanted in the corresponding place in the equation.

using (4,150)

150 = 40 (4) + b

using PEMDAS you find that b = -10

Then plug and chug to find the number of stamps for the 25th term.

y = 40(25) + -10 or y = 40(25) - 10

y = 990

Answer 2

The sequence:
a 1 = 30, a 2 = 70, a 3 = 110, a 4 = 150, a 5 = 190,...
a 2 = a 1 + d
70 = 30 + d
d = 70 - 30 = 40
a n = a 1 + ( n - 1 ) * d
For the 25th month:
a 25 = 30 + 24 * 40 = 30 + 960 = 990
Answer: B ) 990.