# basic maths question

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• Dec 31st 2006, 05:24 PM
obi
basic maths question
We're doing some school holidays maths. Son is 8 yo.

I don't understand the technique for this question..

these 6 numbers can be arr in 3 pairs so they add up to same answer

158 235 318 426 349 266

I've done it the hard way, but im there is a technique here.
• Dec 31st 2006, 05:33 PM
ThePerfectHacker
Quote:

Originally Posted by obi
We're doing some school holidays maths. Son is 8 yo.

I don't understand the technique for this question..

these 6 numbers can be arr in 3 pairs so they add up to same answer

158 235 318 426 349 266

I've done it the hard way, but im there is a technique here.

I do not thing there is an easy way unless guessing which work and do not.
• Dec 31st 2006, 06:01 PM
obi
if this is true then this is too hard for an 8yo. There MUST be a way to work this out. Guessing could take all day.

Quote:

Originally Posted by ThePerfectHacker
I do not thing there is an easy way unless guessing which work and do not.

• Dec 31st 2006, 06:07 PM
ticbol
Quote:

Originally Posted by obi
We're doing some school holidays maths. Son is 8 yo.

I don't understand the technique for this question..

these 6 numbers can be arr in 3 pairs so they add up to same answer

158 235 318 426 349 266

I've done it the hard way, but im there is a technique here.

This is for your 8-yr old son? If so, then let's think like we are 8 years old too, meaning we do not know hard Math yet. We are into addition/subtraction yet mostly.

A pair is two.
So if the sum of the units digit of a pair ends up as the same for all 3 pairs, then we might get the same sum for the 3 pairs?

The six units digits are 8, 5, 8, 6, 9, 6.
Adding any two that might give the same last number, or the sum's units digit, might solve the problem.
6+8 = 14, and 5+9 = 14.
The units digit of both sums is same 4. Umm, maybe good.

Then,
235 +349 = 584
158 +426 = 584
318 +266 = 584

Three pairs, same sum. Good.

------------------
An exercise for sudoku puzzles. :)
• Dec 31st 2006, 06:21 PM
obi
i don't understand. If I don't understand how can an 8 yo?

What is this <sum of the units digit> ?
• Dec 31st 2006, 06:22 PM
ticbol
Quote:

Originally Posted by obi
We're doing some school holidays maths. Son is 8 yo.

I don't understand the technique for this question..

these 6 numbers can be arr in 3 pairs so they add up to same answer

158 235 318 426 349 266

I've done it the hard way, but im there is a technique here.

Another way, although I doubt if an 8-yr old knows the reasoning behind it yet.

There are 6 given numbers to be divided into 3 pairs. Each pair adds up to the same number.

So, add the 6 given numbers, and divide the total by 3 to get that "same number" sum of any pair.
158 +235 +318 +426 +349 +266 = 1752
1752/3 = 584
So any pair should add up to 584.

What is the number to add to 158 to get 584?
Why, subtract 158 from 584, of course.
So, 584 - 158 = 426. Hey!
Hence one pair is 158 and 426.

Go get the other two pairs.
• Dec 31st 2006, 06:29 PM
ticbol
Quote:

Originally Posted by obi
i don't understand. If I don't understand how can an 8 yo?

What is this <sum of the units digit> ?

I see.

Okay. In 235, the last number, the 5, is the units digit.
(the first number, the 2, is the hunhreds digit; the 3 is the tens digit)
(Hundreds digit, tens digit, units digit -----for a number with 3 digits. May I assume your son understands a digit?)

So "sum of the units digits" of "235 +349" is 5+9. Which is 14. Then the units digit of this 14 is 4.
• Dec 31st 2006, 06:31 PM
obi
thank you.

we got this maths from a book for year 4 students. I find it's too advanced for an 8 yo.
• Dec 31st 2006, 06:43 PM
ticbol
Quote:

Originally Posted by obi
thank you.

we got this maths from a book for year 4 students. I find it's too advanced for an 8 yo.

I see again. I see he is not yet a Year-4 student.

Pushing the son too early?
Is he a gifted one, though?

• Dec 31st 2006, 06:45 PM
obi
he is going into year 4 from year 3 last year.

he is just a normal brain!
• Dec 31st 2006, 06:49 PM
ticbol
Quote:

Originally Posted by obi
he is going into year 4 from year 3 last year.

he is just a normal brain!

Oh, I see again.

Then good luck to him. Be patient. With you there helping him, he will learn.

Happy New Year!
• Dec 31st 2006, 08:47 PM
ThePerfectHacker
Quote:

Originally Posted by obi
he is just a normal brain!

As a parent of six, I know from experience, never tell him yet. He needs to know that he is talented. When he reaches the right age he is going to know he is average.
• Jan 19th 2007, 10:12 AM
TheBrain
I don't think anyone has said this; forgive me if they have.

Isn't it a case of just being able to put the numbers in order? Put them in order, and then take the biggest and the smallest and pair them up. Then the next biggest and the next smallest... There is no need to do any adding or even know what the totals are.
• Jan 19th 2007, 10:33 AM
ticbol
Quote:

Originally Posted by TheBrain
I don't think anyone has said this; forgive me if they have.

Isn't it a case of just being able to put the numbers in order? Put them in order, and then take the biggest and the smallest and pair them up. Then the next biggest and the next smallest... There is no need to do any adding or even know what the totals are.

Umm, just asking, if you don't do any adding, how will you know the sums are the same?
• Jan 19th 2007, 11:00 AM
TheBrain
Well they just have to be. If you're told that the numbers will pair up, then the smallest one has to go with the largest and so on. If the largest one went with anything other than the smallest, then there wouldn't be a number to go with the smallest one to make it add up.
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