Q&A - P4 Math

[doraemo]

Can someone help me with this ?


Ray and Serene have a total of $1183 in their savings accounts. Serene and Tim have a total of $1124 while Ray and Tim have a total of $961.
How much savings does Tim have?

[Charnic]

doraemo:

Can someone help me with this ?


Ray and Serene have a total of $1183 in their savings accounts. Serene and Tim have a total of $1124 while Ray and Tim have a total of $961.
How much savings does Tim have?

R+S = 1183 ----------(1)
S+T = 1124 ---------- (2)
R+T =961 ------------- (3)
Add 2 and 3
R+S+2T = 2085
Compare the new equation to 1
1183+2T = 2085
2T = 902
T = 401

[doraemo]

Thank you, CNS!

[doraemo]

Here’s another one:-

A class has an equal number of boys and girls. ½ of the boys do not wear glasses and 15 girls do not wear glasses. 12 of the pupils wear glasses. How many pupils are there in the class?

[Charnic]

doraemo:

Here's another one:-

A class has an equal number of boys and girls. ½ of the boys do not wear glasses and 15 girls do not wear glasses. 12 of the pupils wear glasses. How many pupils are there in the class?

Is the answer 36 ? If so, below is the working :

U + [] = 12
[] + 15 = 2U
[] = 2U - 15
Substituting the 3rd equation into the first, you would get :
U + 2U - 15 = 12
3U = 27
U = 9
Boys + girls add up to 4U

[doraemo]

Thank you, CNS…you’re great!

[Charnic]

doraemo:

Thank you, CNS..you're great!

No issue. Tell you something. I seem to derive more satisfaction solving maths now than to teach my own child. Her \" care-less\" attitude is driving me mad :nunchuk:

[doraemo]

hi CNS, any model drawing to solve this solution?

[Charnic]

doraemo:

hi CNS, any model drawing to solve this solution?

I dun know how to post the drawing, but it goes like this :

1) Draw two boxes ( gal and boy ) the same length - cos they are equal
2) For gals, just cut a portion, shade it and mark 15
3) For boys, cut equally into 2 portion and mark U on each and shade only one

Then you would see the unshaded portions are :

One U from boys and one unknown portion [] which equates 12.
For the gals model, yo would know [] + 15 = 2U ( cos they are the same length with boys).

Hope the above is clear ?

[doraemo]

hi CNS,

will get my DD to try… thank you !!!