At 2:00 P. M., a radio announcer reported that the temperature was 25°C. From 11:00 A. M. To 2:00 P. M. The temperature had risen 4°C. From 8:00 A. M. To 11:00 A. M. The temperature had risen 3°C. What was the temperature at 8:00 A. M.?

The temperature at 8:00 A.M. was 18º C.

Step-by-step explanation:

Given that at 2:00 P.M., a radio announcer reported that the temperature was 25 ° C, and that from 11:00 A.M. to 2:00 P.M. the temperature had risen 4 ° C, while from 8:00 A.M. to 11:00 A.M. the temperature had risen 3 ° C, to determine what was the temperature at 8:00 A.M. the following calculation must be performed:

25 - 4 - 3 = X

21 - 3 = X

18 = X

Thus, the temperature at 8:00 A.M. was 18º C.

step-by-step explanation:

first, eliminate the parenthesis:

3

x

+

2

−

4

x

second, group like terms:

3

x

−

4

x

+

2

third, combine like terms:

(

3

−

4

)

x

+

2

→

−

1

x

+

2

→

−

x

+

2

answer: c, the green line

step-by-step explanation:

there is no black line, eliminate b.

simple interest implies periodic payments, but the red line shows no payments, eliminate d.

simple interest has equal payments. if paid say every day, the graph is about a straight line (actually a stairstep).

the yellow line is not straight, eliminate a.

check: the green line is straight, answer is c.

simple interest with positive interest rate gives a straight line sloping up to the right. green line:

g(t) = $100 + ($200-$100) ÷ (20 years) × (t years)

= $100 + (4%/year) × ($100)(t years)

incidentally, the yellow line curving upward represents continuously compounded interest

y = $100 × 2^(t years / (14 assuming the yellow line hits $200 at 14 years. 2^0 is 1, so y(0) = $100; 2^(14/14) is 2, so y(14) = $200.