Q&A - PSLE Math

[tianzhu]

P5G:

Uncle Tianzhu,

Thank you for your clear explanations. So for the log cake, we are talking about a 'whole' log cake and not just 7/8.

Will the answer be just 1/3 if \"of a\" is removed from the question as follows:
Nomee distributed 7/8 log cake equally among her twin sister and 2 brothers. What fraction of the log cake did each of them receive?

Hi P5G

Good Morning.

Nomee distributed 7/8 of a log cake equally among her twin sister and 2 brothers. What fraction of the log cake did each of them receive?

In this question, having some form of pictorial representation does help one to see the relationship.

This question touches on “Product of Proper Fractions” which is covered in P5.

Students who are familiar with it can write a number sentence 7/8÷3 or 7/8*1/3 and arrive at an answer of 7/24.

If you rewrite the question as

Nomee ate 1/8 of a log cake and distributed the remainder equally among her twin sister and 2 brothers. What fraction of the remaining part of the log cake did each of them receive?

The answer is 1/3.

Usually, you'll be asked to find the fraction of a whole.

Best wishes

[KSP]

Hi need help here. Thanks.


Lily is meeting a friend at a certain time. If she drives at 80km/h, she will be 1/3 hr late. If she drives at 60km/h, she will be 3/4hr late. How long will the journey take if she drives at 90km/h?

[corneyAmber]

KSP:

Hi need help here. Thanks.


Lily is meeting a friend at a certain time. If she drives at 80km/h, she will be 1/3 hr late. If she drives at 60km/h, she will be 3/4hr late. How long will the journey take if she drives at 90km/h?

Yo KSP! Why are you doing PSLE now? :?

[corneyAmber]

Distance = speed x time

80 x (u+1/3) = 60 x (u+3/4)
80u + 80/3 = 60u + 45
20u = (135-80)/3
20u = 55/3
u = 55/60 = 55 mins

1/3 hr = 20 mins
3/4 hr = 45 mins

so distance = 80 x (55/60 + 20/60) = 100km
check: distance = 60 x (55/60 + 45/60) = 100km
So if speed =90km/h
time = 100/90 h = 1 1/9h.

[Dharma]

When distance is fixed; speed and time are inversely proportional.

Speed ratio => 80 : 60 = 4 : 3
Time ratio => 3: 4
4u – 3u = 1u = (3/4 – 1/3) = 5/12 hrs
Total distance = 80 x 3 x 5/12 = 100km
Time taken when speed is 90km/hr = 100/90 = 10/9 hrs

[corneyAmber]

Dharma:

When distance is fixed; speed and time are inversely proportional.

Speed ratio => 80 : 60 = 4 : 3
Time ratio => 3: 4
4u – 3u = 1u = (3/4 – 1/3) = 5/12 hrs
Total distance = 80 x 3 x 5/12 = 100km
Time taken when speed is 90km/hr = 100/90 = 10/9 hrs

I like this shorter approach! :imcool:

[Dharma]

ksi:

Dharma:

When distance is fixed; speed and time are inversely proportional.

Speed ratio => 80 : 60 = 4 : 3
Time ratio => 3: 4
4u – 3u = 1u = (3/4 – 1/3) = 5/12 hrs
Total distance = 80 x 3 x 5/12 = 100km
Time taken when speed is 90km/hr = 100/90 = 10/9 hrs

I like this shorter approach! :imcool:

Glad you like it, ksi.

[KSP]

ksi:

KSP:

Hi need help here. Thanks.


Lily is meeting a friend at a certain time. If she drives at 80km/h, she will be 1/3 hr late. If she drives at 60km/h, she will be 3/4hr late. How long will the journey take if she drives at 90km/h?

Yo KSP! Why are you doing PSLE now? :?

i'm preparing myself ahead..... thanks.

[KSP]

Dharma:

ksi:

[quote=\"Dharma\"]When distance is fixed; speed and time are inversely proportional.

Speed ratio => 80 : 60 = 4 : 3
Time ratio => 3: 4
4u – 3u = 1u = (3/4 – 1/3) = 5/12 hrs
Total distance = 80 x 3 x 5/12 = 100km
Time taken when speed is 90km/hr = 100/90 = 10/9 hrs

I like this shorter approach! :imcool:

Glad you like it, ksi.[/quote]thanks to both of u...

[P5G]

Please help.


Paya Lebar Methodist Girls' Prelim Question 15.
http://www.orlesson.org/orp/09Ma/2009-P6-Math-SA2-PLMGS.pdf


The following pattern is created with 4 letters, A, B, C and D.

ABCDAABBCCDDAAABBBCCCDDD.................?
..............................................24th 230th

Following the above pattern, what is the 230th letter?

(1) A
(2) B
(3) C
(4) D


Given answer is (1).


TIA.