the number number will be even
Common difference is 8
an = a1 + d(n-1)
a15 = 1 + 8(15-1)
a15 = 1+ 8*14
a15 = 1 +112
a15 =113
double it 226
even number
The answer to the first is 4/15x and the second is x+5
When x is doubled, y is doubled. When z is multiplied by 5/8, so is y. The result of both changes is that y is multplied by 2·(5/8) = 5/4. The new value of y is
... y = 5/4·320 = 400
_____
If you really want to, you can use the formula
... y = kxz
and compute the value of k as
... k = y/(xz) = 320/(4·16) = 5
Then use this formula with the new values of x and z:
... y = 5·8·10 = 400
The answer is the surface area will be 440 square inches less.
The answer is 12.5 the reason is due to base x height equals width so multiply the base which is 6 by a number until you get 75 which is just 12.5