SOLUTION: The formula R=-0.075t+3.85 can be used to perdict the world record in the 1500 meter run, t years after 1930. Determine an inequality that identifies the year in which the world re

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Question 477058: The formula R=-0.075t+3.85 can be used to perdict the world record in the 1500 meter run, t years after 1930. Determine an inequality that identifies the year in which the world record will be less then 3.4 minutes.
solve for t
t>?

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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The formula R=-0.075t+3.85 can be used to predict the world record in the 1500 meter run, t years after 1930.
Determine an inequality that identifies the year in which the world record will be less then 3.4 minutes.
solve for t>
:
-0.075t + 3.85 < 3.4
;
-0.075t < 3.4 - 3.85
:
-0.075t < - .45
Get rid of the negative t, multiply both sides by -1, the reverses the inequality sign
.075t > .45
t > .45%2F.075
t > 6 yrs after 1930
We can say that in 1937, the record will be less than 3.4 min
:
:
Check this. Find the record in 1937, (t=7)
r = -0.075(7) + 3.85
r = -.525 + 3.85
r = 3.325 min in 1937 just under 3.4