The sum of 2 consecutive numbers is 21. Which equation below can be used to find the numbers?

Answer 1

Where are the equations you're referring to?

OK, these are two consecutive numbers, meaning the second is one more than the first.

So n + (n + 1) = 21

2n + 1 = 21

2n + 1 - 1 = 21 - 1

2n = 20

Divide both sides by 2, and

n = 10

And 10 and 11 are consecutive numbers!

Answer 2

WHEN ASKED ABOUT CONSECUTIVE NUMBERS CONSIDER WHAT A CONSECUTIVE NUMBER IS.... TWO NUMBERS RIGHT AFTER ANOTHER...

EXAMPLE
WHEN YOU COUNT YOU COUNT LIKE THIS....
1 2 3 4 5 6 7

THIS MEANS 1 AND 2 ARE CONSECUTIVE
5 AND 6 ARE CONSECUTIVE
ETC....

NOTICE EACH CONSECUTIVE NUMBER IS 1 LARGER.

LET X= FIRST CONSECUTIVE NUMBER
SINCE THE NEXT NUMBER IS ONE NUMBER LARGER THE SECOND CONSECUTIVE NUMBER IS REPRESENTED AS X + 1

SO THE TWO NUMBERS ARE X AND X+1

SINCE THERE SUM IS 21 SHOW AN EQUATION WHERE THEY ARE ADDED AND SET IT EQUAL TO 21

X + (X + 1) = 21
SIMPLIFY
X + X IS 2X YOU GET:

2X + 1 = 21

sOLVE BY SUBTRACTING 1 ON BOTH SIDES
2X = 20
DIVIDE BY 2 ON BOTH SIDES
X = 10

nOW IF YOU WANT TO KNOW WHAT THOSE NUMBERS ARE....

YOUR TWO CONSECUTIVE NUMBERS WERE:
X
X+1

sUBSTITUTE X = 10 IN EACH EQUATION

X = 10
X + 1 = (10) + 1 = 11

YOUR TWO CONSECUTIVE NUMBERS ARE 10 AND 11

10 + 11 = 21 SO THIS SHOWS YOUR TWO EQUATIONS X AND X + 1 WORK OUT.

Answer 3

10+11=21

Answer 4

Let x = the 1st consecutive number.
Let x + 1 = the 2nd consecutive number.

so,

x + (x+1) = 21

2x + 1 = 21

2x = 20

x = 10
and
x+1 = 11

Answer 5

let one number be x
2nd number = x + 1
so,
x+(x + 1) = 21
2x + 1 = 21
- 1 = -1

2x = 20
x = 10
so, fist number is 10 and the second number is 11.

Answer 6

number 1 is x
number 2 is x+1
sum is 21
x+x+1=21
2x = 20
x=10
x+1=11

Answer 7

x
x+1
x+x+1=21
2x+1=21
2x=20
x=10