## Order of operations isn't working.

Simplificatation, evaluation, linear equations, linear graphs, linear inequalities, basic word problems, etc.
lottsm
Posts: 2
Joined: Wed Jul 06, 2016 2:13 pm
Contact:

### Order of operations isn't working.

Q = 1,500 – 4P + 5A + 10I + 3PX

P = \$400
A = \$20,000
I = \$15,000
PX = \$500

pemdas
Q = 1500 – 4 * 400 + 5 * 20000 + 10 * 15000 + 3 * 500
Q = 1500 – (4*400) + (5*20000) + (10*15000) + (3*500)
Q = 1500 – 1600 + 100000 + 150000 + 1500
Q = 1500 – 253100 = -251600 this is my answer, but I understand that it should be 251400. What am I missing?

Posts: 136
Joined: Sun Feb 22, 2009 11:12 pm

### Re: Order of operations isn't working.

Q = 1,500 – 4P + 5A + 10I + 3PX

P = \$400
A = \$20,000
I = \$15,000
PX = \$500

pemdas
Q = 1500 – 4 * 400 + 5 * 20000 + 10 * 15000 + 3 * 500
Q = 1500 – (4*400) + (5*20000) + (10*15000) + (3*500)
Q = 1500 – 1600 + 100000 + 150000 + 1500
Q = 1500 – 253100...
Without any grouping symbols telling you to, why did you "distribute" the "minus" from the "1600" onto the terms that followed it? You did:

. . .1,500 - (1,600 + 100,000 + 150,000 + 1,500) = 1,500 - 1,600 - 100,000 - 150,000 - 1,500

But this isn't what they gave you.

lottsm
Posts: 2
Joined: Wed Jul 06, 2016 2:13 pm
Contact:

### Re: Order of operations isn't working.

I don't understand math; that's why I'm here. I thought that I was doing pemdas exactly...addition comes before subtraction. It seems to me that I'm doing exactly what they gave me.

nona.m.nona
Posts: 288
Joined: Sun Dec 14, 2008 11:07 pm
Contact:

### Re: Order of operations isn't working.

I don't understand math; that's why I'm here. I thought that I was doing pemdas exactly...addition comes before subtraction. It seems to me that I'm doing exactly what they gave me.
No. As explained in (this) lesson, addition and subtraction are at the same "level" and are done at the same time, from left to right. There is no "distribution", even were addition to come "first" in some manner, which it does not. The "plus" signs in front of the final three terms do not become "minus" signs simply because a prior term had a "minus" sign; they retain their additive aspect.

You may wish to review number properties (here) -- specifically, the commutative property of addition -- to understand why "-1,600 + 100,000 + 150,000 + 1,500" is the same as "100,000 + 150,000 + 1,500 - 1,600", and is never equal to -100,000 - 150,000 - 1,500 - 1,600.

If you have further questions, please be specific. Thank you.