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5 votes
Rafael is driving to Los Angeles. Suppose that the distance to his destination (in miles) is a linear function of his total driving time (in minutes). Rafael has 62miles to his destination after 16 minutes of driving, and he has 41.1 miles to his destination after 38 minutes of driving. How many miles will he have to hisdestination after 42 minutes of driving?

1 Answer

5 votes

Since the distance d is a linear function of his total driving time t, we can write:

d = at + b

with a and b constants.

Now, for d = 62, t = 16. So:

62 = a * 16 + b

Also, for d = 41.1, t = 38. So:

41.1 = a * 38 + b

Then, we can use those two equations two find the values of a and b, and then find the distance d when t = 42.

From the first equation, we obtain:

62 = a * 16 + b

62 - 16a = b

Now, we can use this expression for b into the second equation to find a:

41.1 = a * 38 + b

41.1 = 38a + 62 - 16a

41.1 = (38 - 16)a + 62

41.1 = 22a + 62

22a = 41.1 - 62

22a = -20.9

a = -20.9/22

a = -0.95

Now, we can use the value of a to find b:

b = 62 - 16a

b = 62 - 16 * (-0.95)

b = 62 + 15.2

b = 77.2

Thus, the relation between d and t is:

d = -0.95t + 77.2

Then, using t = 42, we find:

d = -0.95 * 42 + 77.2

d = -39.9 + 77.2

d = 37.3

Therefore, after 42 minutes of driving, he will have 37.3 miles to his destination.

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