Lesson: Operations with Signed Numbers - Part I

Reinforcement Activities

Comment on Operations with Signed Numbers - Part I

bimla - July 30, 2017
I needed this basic as I have been out of school for a long time

bryant2086 - June 29, 2021
Just wanted to say that I appreciate you providing these Reinforcement Activities with each lesson. Even though it's been 18+ years since I've taken high school math, fundamentally I understand these rudimentary elements. It's the way the GRE words their questions is what really throws me off. It's almost like I have to learn to speak and comprehend the "GRE language" before I can really excel at the test.
greenlight-admin's picture

greenlight-admin - June 30, 2021

That's an astute observation. There are many GRE quantitative questions that seem to test students' reading comprehension skills more than their math skills.

mwahabsultan - July 5, 2022
I have a problem with addition in this question from above.....https://gre.myprepclub.com/forum/in-the-addition-problem-above-the-number-must-be-28526.html

Your reply:
When we replace each * with 5, the addition doesn't work.
When we replace each * with 6, the addition works!

My question what i don't understand why doesn't the addition work like is there a rule or something.like 4 + 5 + 5 = 14 but we accepted 4 + 6 + 6 = 16 Why?
greenlight-admin's picture

greenlight-admin - July 5, 2022

Question link: https://gre.myprepclub.com/forum/in-the-addition-problem-above-the-numbe...

Sorry, but I'm not quite sure I understand what you're asking. Can you please rephrase your question?

In the meantime, I'll explain a little bit more about what the question is asking just in case this is where you're having difficulties.

In the question, we're adding three 3-digit values to get a 4-digit sum.
We're told 734 + 5*8 + 9*2 = 22*4

The idea here is that each * represents the same digit for all 3 values in the sum.
Note: the * symbol does not represent multiplication.

So, for example, if * = 1, then our sum becomes 734 + 518 + 912 = 2214
Note: 734 + 518 + 912 does not equal 2214, so * = 1 does not make the equation true.

If * = 6, then our sum becomes 734 + 568 + 962 = 2264 (works!)

Does that help?

mwahabsultan - July 7, 2022
Oh as it represents same digit so if we do 5 + 5 + 4 we get 14 not 15 but 6 + 6 + 4 we get 16 as 6 in tens place and *'s have 6 so same digit as added.....oh that's a sneaky one
greenlight-admin's picture

greenlight-admin - July 7, 2022

That's right.

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