Question

An online data base charges $25 an hour during the day and $12.50 an hour at night. If a research company paid $250 for 12 hours of use, which system of equations could be used to determine the number of hours charged at the day rate (d) and at the night rate (n)?

Answer 1

Answer

Find out the  which system of equations could be used to determine the number of hours charged at the day rate (d) and at the night rate (n) .

To proof

As given in the question

Let us assume that the number of hours charged at the day rate = d

Let us assume that the number of hours charged at the night rate = n

An online data base charges $25 an hour during the day and $12.50 an hour at night. If a research company paid $250 for 12 hours of use.

Total working hour in a company including day and night be  12 hours .

than the equation become in the form

d + n = 12

also

An online data base charges $25 an hour during the day

$12.50 an hour at night.

If a research company paid $250 for 12 hours of use.

than the equation becomes

25d + 12.50n = 250

than the two equation are

d + n = 12 , 25d + 12.50n = 250

multiply first by 25 and subtracted  from 25d + 12.50n = 250

25d - 25d + 12.50n - 25n = 250 - 300

12.5 n = 50

$n = \frac{50}{12.5}$

n = 4hours

put this in the d + n = 12

d + 4 =12

d = 12-4

d = 8 hours

Therefore the number of hours charged at the day rate  is 8 hours  and at the night rate is  4hours .

Hence proved