Question #55dec

3 Answers
Dec 3, 2017

The numbers are #14 and 18#

Explanation:

You can choose whether to use one or two variables.

I will use one variable and write the second number in terms of the first.

Let the smaller number be #x#
The larger number is #x+4# (They differ by #4#)

The sum is 32. Write an equation:

#x+x+4 =32#

#2x = 28#

#x=14#

The numbers are #14 and 18#

#18-14=4 and 14+18 = 32#


However, a question like this can be done by logic as well.

You know what the sum of the numbers is, and that one number is #4# more than the other.

Subtract the difference between them from #32# first.
#32-4 = 28#

This now has to be the sum of two equal numbers:
#28 div 2=14#

The one number is #14# and the other is #4# more, ie #18#

If you look at the process in this thinking, you will see that is exactly what was done with the algebra.

#18# and #14#

Explanation:

There are 2 ways you could solve this. The first is the proper way, but if it's with simple numbers, I use the second way. I'll show you both.

1st Way:

Let #x# and #y# be the two numbers.

Difference of #4:" "x-y=4#
The Sum is #32:" "x+y=32#

If we add the two equations together, we get:
#2x=36#

We can simplify this to:
#x=18#

By substituting #x# into either of the initial equations, we get:
#18+y=32#
#y=14#.

2nd Way:
Since the numbers are pretty small, I would do it like this mentally:

We know we need two numbers that add up to 32. Let's divide 32 by 2:

#32/2 = 16#.

Now, the difference between those two numbers is #4#.
So if we #+-2# to each side, we would get a difference of #4#.

#16+2=18#
#16-2=14#

Don't you think this is faster?!

But you should always know how to solve it using the first method as that is pure algebra.

Dec 3, 2017

#a = 18#
#b = 14#

Explanation:

Let #a# and #b# represent the two numbers.

Because you have two numbers, you will need two equations to find them.

Given in the problem are the following two equations:

1) The sum of #a# and #b# is #32#
#a + b = 32#

2) The difference between #a# and #b# is #4#
#a - b = 4#

Add the equations to let the #b# term drop out to zero

. .#a + b = 32#
+ #a - b =   4#
....................................
.#2a . . . . = 36#

#a = 18# #larr# answer for #a#

If #a = 18,# then #b = 14# #larr# answer for #b#

Answer:
#a = 18#
#b = 14#
~ ~ ~ ~ ~ ~ ~ ~

Check
. #a +   b = 32#
#18 + 14 = 32#  ✓

. #a -  b  = 4#
#18 - 14 = 4#  ✓