For sake of convenience, reverse the series, then it would be:
21,19,17.....7
a=21, d = -2,
s(4) = 4/2 (21+15)
s(4)=2(36)
s(4) = 72
Answer:
Find the unit rate of each printing machine and compare.
Step-by-step explanation:
Answer:
C. $97
Step-by-step explanation:
The average of his wage for all 15 days is the sum of all wages for the 15 days divided by 15.
average wage for 15 days = (sum of wages for the 15 days)/15
The amount of wages during a number of days is the product of the average wage of those days and the number of days.
First 7 days:
average wage: $87
number of days: 7
total wages in first 7 days = 7 * $87/day = $609
Last 7 days:
average wage: $92
number of days: 7
total wages in last 7 days = 7 * $92/day = $644
8th day:
wages of the 8th day is unknown, so we let x = wages of the 8th day
total wages of 15 days = (wages of first 7 days) + (wages of 8th day) + (wages of last 7 days)
total wages of 15 days = 609 + x + 644 = x + 1253
average wage for 15 days = (sum of wages for the 15 days)/15
average wage for 15 days = (x + 1253)/15
We are told the average for the 15 days is $90/day.
(x + 1253)/15 = 90
Multiply both sides by 15.
x + 1253 = 1350
Subtract 1253 from both sides.
x = 97
Answer: $97
