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If a, b, c, d are four consecutive whole numbers and a + b + c +d =78. find the value of c.​

User Asvd
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1 Answer

8 votes

Answer: 20

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Step-by-step explanation:

a,b,c,d are consecutive whole numbers. This means one follows right after the other. Example: 5,6,7,8 or 50,51,52,53

In general we have:

  • a = some whole number
  • b = a+1
  • c = b+1 = (a+1)+1 = a+2
  • d = c+1 = (a+2)+1 = a+3

The sequence a,b,c,d is the same as a,a+1,a+2,a+3

Add those expressions together and set the sum equal to 78. Then solve for 'a'.

a+b+c+d = 78

a+(a+1)+(a+2)+(a+3) = 78

4a+6 = 78

4a = 78-6

4a = 72

a = 72/4

a = 18

This leads to

  • b = a+1 = 18+1 = 19
  • c = a+2 = 18+2 = 20 which is the answer
  • d = a+3 = 18+3 = 21

The four consecutive whole numbers for a,b,c,d are 18,19,20,21 in that order.

As a check,

a+b+c+d = 18+19+20+21 = 78

which confirms our answer.

User Djvg
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