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If you double a number and then add 28 ​, you get 4/9

of the original number. What is the original​ number?

User Peacetype
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1 Answer

6 votes

Answer: -124/9 or -13.778

Step-explanation: You may not have any idea how to approach this problem but I can help. We are given some information about a number and asked to find out what number it is. Since we don't know what the number is, we can say that it is X (a variable).

If you double X and add 28 you get 4/9. Doubling X can be represented as 2X. If we add 28 to that, we get 2X+28. We are told we get 4/9 which means that 2X + 28 is equal to 4/9 or 2x + 28 = 4/9.

We have now built an algebraic equation for X. We can now simply solve for X.

2X + 28 = 4/9

2X + 252/9 = 4/9 Rewrite 28 as 252/9 so we have common denominators

2X = -248/9 Subtract 252/9 from both sides

X = -124/9 Divide by 2 on both sides and we get X

Whenever you are given a problem similar to this one, try to create an algebraic equation or expression that can model the problem. A variable can represent the number you are trying to find.

Hope this helps!

User DSchmidt
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