Question

Find a number whose product with 8 is the same as its sum with 49. (Hint: you may want to try guess and check or use a table.)


8

7

6

9

Answer 1

Here, I would prefer using actual Algebra.
Let's call the unknown number "x." Then, we can write the problem in a more mathematical way:
8x (the product of this number and 8)
x + 49 (the sum of this number and 49)

They're equal, so we set them equal to each other and solve for our number:
8x = x + 49

Answer 2

From here, all we have to do is subtract off the x from both sides to get the x-terms alone:
8x - x = x + 49 - x
7x = 49

Then divide by 7:
x = 7

Answer 3

Otherwise, if we really wanted to guess and check, we'd just use those two expressions:
8* a number
a number + 49

and plug in each answer choice to see which one works. I prefer using the Algebra, though, since its more concise and gives a direct answer. :P

Answer 4

x = that number
So 8x = x+ 49
7x = 49
x = 7

So the number is 7. No offense, but guess and check in this problem is a pretty stupid thing to do when it's so easy to solve it algebraically.

Answer 5

If you want to use guess and check though, since it's MC just plug in the values

8(8) = 8 + 49
64 = 57, no, so it's not 8

8(7) -we already know that works

8(6) = 6 + 49
48 = 55, no, so it's not 6

8(9) = 9+49
72 = 58, no, so it's not 9