Tuesday, October 21, 2008

Singapore Math 4

Attempted to solve by models 2 questions Monica put forth in the comments section of the previous post. Please let me know if I'm getting any closer to model mode.

1. Maria sold thrice as many $5 files as $10 files. She also sold twice as many $10 files as $20 files. She collected $160 more from selling $5 files than from selling $20 files.
a) How much did she collect from selling $5 files?
b) How many files did she sell altogether?




2. Joyce is 4 years old. Her mother was 25 years older than her last year.
a) In how many years' time will Joyce's age be 2/7 of her mother's age?
b) In how many years' time will Joyce's age be 3/8 of her mother's age?

Answer:

Note: The difference between the ages of Joyce and her mother is constant at 25 years.

5 comments:

monlim said...

Excellent!! See? You're getting it already! Your answers to both questions are right. Model for Q1 is perfect. For Q2, just need to tweak your model, ie Joyce and Mother shd be 2 different rows. Eg for part a), draw Joyce for 2 parts, draw her mother below that wit 7 parts and the 5 parts that are longer than Joyce is 25.

Lilian said...

Thanks Sifu, aiyoh, crack my head so long for Q1. More questions please, hehe...don't you wish our kids asked for more practice questions like I do? Why can't they have such good attitudes :)

monlim said...

I also say! I'm always raring to try the problem sums in Lesley-Anne's assessment books, but must sweet talk her into doing and then she gives up so quickly some more...

monlim said...

Since you asked for it, here's a couple more (from p5 EPH Challenging Maths).

1) There were some red, blue and green jelly beans in a bag. The number of red jelly beans was 2 1/3 times the number of green jelly beans. The number of blue jelly beans was 0.5 times the total number of red and green jelly beans. When 200 jelly beans were added into the box, the number of green beans became 1.5 times the original number of green jelly beans, the number of red jelly beans was increased by 1/7 and the number of blue beans was increased by 50. Find the total number of jelly beans in the bag in the end.

2) 2/3 of the number of shells Sheba collected is equal to 3/8 of the number of shells Ann and Dick collected together. Ann collected 1/3 as many shells as Dick.
a) What percentage of the total shells did Ann collect?
b) Express the number of shells Dick collected as a percentage of the number of shells Sheba collected, correct to 2 decimal places.
c) If Dick collected 72 shells more than Sheba, how many shells did the 3 children collect in all?

I hope I typed everything correctly!!

Anonymous said...

Cool! You figured out the model to the 2nd part of Q1 when I couldn't.

YY.