Answer: 12
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Work Shown:
x = first number
x+1 = second number
x+2 = third number
x+3 = fourth number
x+4 = fifth number
Note how the numbers are one after another. Consecutive numbers follow this pattern. For example: 6,7,8,9,10 are consecutive numbers. One number follows right after the other.
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Add up those five expressions. Set the sum equal to 70 and solve for x
(x)+(x+1)+(x+2)+(x+3)+(x+4) = 70
(x+x+x+x+x)+(1+2+3+4) = 70
5x+10 = 70
5x = 70-10
5x = 60
x = 60/5
x = 12 is the first number and the smallest number
x+1 = 12+1 = 13 is the second number
x+2 = 12+2 = 14 is the third number
x+3 = 12+3 = 15 is the fourth number
x+4 = 12+4 = 16 is the fifth number
Check:
12+13+14+15+16 = 70
which confirms our answer
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You could use a guess and check method, but the algebraic approach is much more efficient.