This is the sum of the arithmetic sequence:
10 - 2 + 6 + 14 + ... + 110
where: a 1 = - 10, d = 8
a n = 110
a n = a 1 + ( n - 1 ) * d
110 = - 10 + ( n - 1 ) * 8
110 = - 10 + 8 n - 8
110 + 10 + 8 = 8 n
128 = 8 n
n = 128 : 8
n = 16
∑ n = n/2 * ( a 1 + a n )
∑ 16 = 16/2 * ( -10 + 110 ) = 8 * 100 = 800
Answer:
The sum is 800.
Commutative Property is used here
1/6 students in the school chorus are in fourth grade
Answer:
27
Step-by-step explanation:
Let x represent the number of $0.15 stamps Ivan bought. Then the value of his stamps is ...
0.15x +0.40(35-x) = 7.25
-0.25x +14.00 = 7.25 . . . . . eliminate parentheses, collect terms
-0.25x = -6.75 . . . . . . . . . . . subtract 14.00
x = 27 . . . . . . . . . . . . . . . . . . divide by -0.25
Ivan bought 27 $0.15 stamps.
