Units and parts question. Let the initial ration of 1:3 be in units, and the final ration of 7:9 be in parts 1 unit + 15 = 7 parts 3 units - 15 = 9 parts To find the value of 1 unit or 1 part, we must eliminate the other. It is easier to elimiate units in this case. By multiplying '3' on both sides of the first equation, we will get: 3 units + 45 = 21 parts Notice that there is a "3 units" in both equations now. So we can eliminate units just by subtracting one equation from another. Now, if we were to subtract the second equation from this equation that we just obtained, 45 - (-15) = 12 parts 60 = 12 parts 1 part = 5. Since there are 9 parts of girls left, No of girls left = 9x5 =45 No of girls at first=45+15, = 60.

Thanks, Shu Hao😊

Consider what remains the same. The total number of children is the same cos 15 left and 15 joined. So before is 1:3. Total 4 units. After 7:9. Total 16 units. Make total number is units the same. 1:3 (multiply by 4) = 4:12 3 units = 15.

Hmm... Didnt think of that lol

Make total of units the same. Typo. So 3 units = 15. 12 units = 15 × 4 =60 girls at first.

Thanks, Yueh Mei😊

The model is quite correct but the method is simultaneous equations. My take is to solve heuristically. The amt they spent 475-370=105 Take this as a set, 3 sets = 315 370-315= 55 (1 unit of A - left) A: 5 units at first = 5 x 55 B : 475 - A (above)

Thanks Vera Koh and Gerald Goh!

Lol 9k years old... 😂 scared me when i first read it 😱

Anyways... a) Nigel = 9k/3 = 3k years old Bryan = 3k-2k= k years old b) When Bryan is 18 years old, k=18 9k=... 162 years old... Hence, Mr. Wong would be 162 years old then. (WHAT???)

Must leav

Thanks but the b) the answer must be in terms of k???

No idea... Whats the given ans?

A School homework given by teacher, no answer...

B) 9k + (18-k) = 8k + 18. ???

b) when Bryan is 18k years old, Nigel will be 20k years old. So 1 unit = 20k 3 units = 20k x 3 = 60k Mr Wong will be 60k years old when Bryan is 18k years old.

Q is when Bryan is 18 years old, not 18k years old leh...

That's the tricky part.

lost!

Bryan is 1k years old now so when he's 18 years old means 1k x 18 = 18k years old

Huh?

Mr Wong is always 8k older than Bryan. So the answer is 8k+18.

Ahh... Kho Tek Hong I see what you mean

A) This year Mr Wong: 9k yo Nigel: 3k yo Bryan: k yo b) when Bryan is 18 yo, it'll be (18-k) years later, so, Mr Wong: 9k+(18-k)=8k+18 Nigel: 3k+(18-k)=2k+18 Bryan: k+(18-k)=18

Thanks all

Sorry all. Kindly ignore part b Ans as my daughter has misread the qn, hence wrong ans.

Thanks

2r+3f=38 2(f+4)+3f=38 f=6kg r=10kg

5u + 8 = 38 5u = 30 1u = 6 Rice = 1u + 4 Rice = 6 + 4 = 10kg

Thanks Carol Khoh... yours is easier for me to explain to my son.. i didnt see the 2 bags of rice total mass is 8kg.. thanks.

Hi, it's the extra weight of the rice that made the 8 kg 😊

2 bags of rice and 3 bags of flour --> 38 kg Replacing 2 bags of rice by 2 bags of flour, 5 bags of flour --> 30 kg 1 bag of flour --> 6 kg 1 bag of rice --> 10 kg

This method is known as proportional reasoning.

Kho Tek Hong.. Your method I like.. Proportional Reasoning.. Its easier to solve if the kids understand the reasoning.. Thanks