Answer 420.
a, is the first term. d is difference.
Since this is an arithmetic progression, I use this formula.
Un = nth term
Sn = sum of terms.
First find the number of terms, which is 20.
Then use the second formula to find the sum.

3 0

3 years ago

The sum of half of a number and 8 less<br> than the number is 25. Find the number.

LuckyWell [14K]

Answer:

The number is 22

Step-by-step explanation:

let x = the number

$\frac{1}{2} x + x - 8 = 25 \\ \frac{1}{2} x + x - 8 + 8 = 25 + 8 \\ \frac{1}{2} x + x = 33 \\ factor \: out\: x \: on \: the \: left \\ x( \frac{1}{2} + 1) = 33 \\ divide \: both \: sides \: by \: \frac{1}{2} + 1 \\ \frac{x( \frac{1}{2} + 1) }{ \frac{1}{2} + 1} = \frac{33}{ \frac{1}{2} + 1} \\ x = \frac{33}{ \frac{3}{2} } \\ x = \frac{66}{3} \\ x = 22$

let's factor out x from the left hand sid

4 0

3 years ago