## Friday, April 29, 2011

### Chapter 4: Algebra... Help! What's Wrong?

Jane did the following:
• 3a + b = 3ab
• 2s + 4t = 6st
Do you think Jane applied the correct algebraic manipulations process?
If yes, please write down examples to show that her answer is correct.

If not, explain to Jane her mistakes and help her to correct.

1. No.

3a + b is 3Xa+b
while
3ab is 3XaXb
which is completely different

and

2s + 4t is 2Xs+4Xt
while 6st is 6XsXt which is also different

2. Farrell nah jun hao4/30/2011 04:00:00 PM

She is not correct. 3a+b=3xa+b while 3ab=3xaxb
2s+4t=2xs+4xt while 6st=6xsxt.

3. No. 3ab is 3xaxb while 3a+b is 3xa+b
2s+4t is 2xs+4xt. 6st is 6xsxt

4. No. 3a=3xa but 3a+b=3xa+b, not 3ab. This is because 3ab is 3xaxb
The same concept applies here. 2s=2xs, 4t=4xt. Therefore, 6st is not the correct answer. The answer is 6xsxt

5. No jane is not correct..
3a + b are completely different variables they cannot be added together unless they multiplied.. which is 3a x b =3ab
This is the correct one .. The same applies for the second one
2s+ 4t..

6. No.

3a + b= 3 x a + b
BUT, 3ab = 3 x a x b
So they cannot be equal.
The same concept can also be applied on the second example.

7. You are all right. In the explanation please use commutative laws of addition and multiplication in your explanation.

8. No.
3ab is 3 x a x b
3a + b is 3 x a +b

these two answers are completely different, so therefore her answer is wrong in both expressions.

9. No.
3a + b is 3 x a + b while
3a + b is 3 x a x b .
(a and b are different and they can't be combined)

It's the same for 2s + 4t
2s + 4t is 2 x s + 4 x t while
6st is 6 x s x t which isn't the same.
(s and t are different and so can't be combined)

10. 3a + b = 3ab
2s + 4t = 6st

There is a big mistake done by the student.
These cant be combined.

--
Vedic Maths Forum India

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12. No.
3a + b = (3xa) + b
2s + 4t is (2xs) + (4xt)

13. No,she is wrong
The answer that Jane gave is not the sum of the numbers but it i the product .

These numbers can only be added if one of the values ( a or b ) is given.

For Example , Take a as 1 and b as 2

A=1
B=2

3a + b = 3+2
=5

3ab on the other hand is 3x1x2 which is 6 so the answer is wrong

This proves that jane is wrong