Q&A - P3 Math

[tianzhu]

Daddy:

Hi,

Thanks. For your input. But the answers are wrong. The correct anwers are 180 sticks for the first question. pattern 30 on the 2nd question.

for 1st question, i did it one by one:
pattern: 1 2 3 4 5 6 7 8
Sticks: 5 10 15 20 25 30 35 40
Total sticks = 5+10+15+20+25+30+35+40 = 180 sticks.

for Q2: I knew it is pattern 30. I found it from the web. But it did not show out it got it.

Hi
Let's us look at the question again.
How many sticks does she need for the eighth pattern?

Does it refer to the number of sticks for the eighth term or the sum of sticks from the first term to the eighth term?From your answer, the latter is more likely.

Every increase in 1 pattern---increase in 5 sticks
Number of sticks---5n, where n is the pattern number.
The number of sticks refers to the total number of sticks from the first term to the nth term, not the number of sticks for the nth term.
The sum is n(5+5n)/2, where n is the term number

To test, consider pattern 1 to 3, the sum is (5+10+15)---30
3(5+15)/2---30
For the sum of sticks from the first pattern to the 4th pattern, we have 4(5+20)/2---50.

For part 1 of the question,from the 1st term to the 8th term,
The total number of sticks---8(5+40)/2---180 sticks.

For part 2, the sum should be 2325 instead of 2350, if the pattern number is 30.

I hope I am leading you to the right path.

btw[quote]I knew it is pattern 30. I found it from the web. But it did not show out it got it. [/quote]It'll be helpful if you could provide the link to this website.Other members may be able to help.

[Daddy]

Hi,


Thanks tianzhu,

How to work out on question 2? What is the step? Thanks.
Here is the web. Just plug in the nos.

http://www.geocities.com/maths9233/Algebra/AP2.html

[tianzhu]

Hi

Is your question replicated in full from your child’s worksheet? If it is, you may want to check with her teacher, the sum of 2350 is incorrect.
How many sticks does she need for the eighth pattern? I think the answer should be 40 because we are talking about the number of sticks for pattern 8.
To find the sum, a more appropriate way to phrase the question will be
How many sticks does she need for the first eight patterns?

Remember this series, Find the sum of (1+2+3+4+5+ …+100).
Your daughter should be able to solve it.Apply this principle for the solution to your question.

Going back to your question, find the pattern number for the sum of sticks which is 2325(not 2350)
Other than Guess and Check, I can’t think of any other way to guide a primary student to arrive at the solution.
Try 10 --------- 10/2(10+45) -------------- 275
Try 20 ---------------------------------------- 1050
Try 30 --------- 30/2(10+145) -------------- 2325, so the answer is pattern 30.

Hope this is of some use to. You may want to share the solution after your daughter receive it from her school.

[Daddy]

Thank tianzhu,


For Q1 you are right, find only the pattern 8. Not sum up from 1st pattern to 8th pattern.

The question is correct. What I think is that use 2350 sticks to make which pattern no. left over sticks are ok.

Try 10 --------- 10/2(10+45) -------------- 275
Try 20 ---------------------------------------- 1050
Try 30 --------- 30/2(10+145) -------------- 2325, so the answer is pattern 30.

Is the above uses AP formular?

Thanks

[tianzhu]

Daddy:

Is the above uses AP formular?

Hi
Leaving some extra sticks is a logical explanation. It depends on how the question is crafted. Is your question an exact replicate from your child’s worksheet or is it being summarised by you?

Yes, it is an AP with a constant difference of 5.But I do not encourage using formulae at this stage. It’s more important to see the relationships in patterns.

Use the same principle as in Find the sum of (1+2+3 ..................+100) to solve your question.

[Daddy]

Thanks tianzhu,


I replicated it my child’s worksheet. I ask the teacher for anwers. Anyway, thanks alot…

[cokepower]

ChiefKiasu:

Here's another one, this time from Catholic High Primary 3 SA1:


Gregory and Timothy has 192 stickers together. After Timothy gave 30 stickers to Gregory, Timothy had thrice as many sticker as Gregory. How many stickers did Gregory have at first?

Again... no algebra please.

T [][][] )
) 192
G[] )

4 units [] = 192
[] = 192/4
[] = 48

Hence T have (48x3)=144, and G have 48

T gives 30 sticker to G

Henceforth G has 30 more and T have 30 less.

Now we have to work backward as we need to find at first.

G 48-30 =18

[michellesim]

Hi all


pls find my model method to solve this question.
http://www.postimage.org/image.php?v=Pq1o56U0

[Daddy]

[Moderator's note: Topics merged.]


Hi,

My daughter have a question, do not know how to do. Please help. Thanks.
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[corneyAmber]

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