Q&A - PSLE Math

[MathIzzzFun]

gijg:

Hi


I got my ds to recheck the question . Here is it , there was some typo error in the 1st q posted .

Mike and Steve started jogging at the same time from pt A and pt B , respectively along a running track in opp direction . Mike met Steve when he is 8km from A . Both of them turn back after reaching A and B . They met again at 4km from B. Find the dist from pt A to pt B . The answer is 20 and none of his frens were able to solve it .

Hi

workings same as this question which was discussed in an earlier thread..http://www.flickr.com/photos/62167097@N02/6085706330/in/photostream

just replaced the numbers ..

http://i54.tinypic.com/r1lb9g.jpg\">

cheers.

[gijg]

Hi MathIzzzFun,


Can you explain the part on 2x8 = 16km. I cannot understand your working from tat pt onwards .

Thanks. You are indeed a genius .

Are u a full time tutor??

[MathIzzzFun]

gijg:

Hi MathIzzzFun,


Can you explain the part on 2x8 = 16km. I cannot understand your working from tat pt onwards .

Thanks. You are indeed a genius .

Are u a full time tutor??

Hi
At first meeting point X, total distance covered = AX (Mike) + XB (Steve) = AB
At 2nd meeting point Y, total distance covered = XB (Mike)+XA(Steve) + BY(Mike) + AY (Steve) = 2 x AB

When total distance travelled is AB, Mike run 8 km; so when total distance is 2AB, Mike run 2 x 8 km = 16km = XB + BY
XB = XY + YB = XY + 4km
so XB + BY = XY + 4km + 4km = 16 km, XY = 16 km - 8km = 8km

cheers.

[ooptimizer]

Appreciate your help in this question - it is a past year PSLE question.


M and L took part in a cycling race. M cycled at a speed of 20km/h. Both of them did not change their speed throughout the race. When L covered half the distance, M was 3.5 km in front of her. M reached the finishing line at 10.45am. What time did L reach the finishing line?

[tianzhu]

ooptimizer:

Appreciate your help in this question - it is a past year PSLE question.


M and L took part in a cycling race. M cycled at a speed of 20km/h. Both of them did not change their speed throughout the race. When L covered half the distance, M was 3.5 km in front of her. M reached the finishing line at 10.45am. What time did L reach the finishing line?

Hi

As in any question on speed, it helps to draw a simple diagram.

When L covered half the race, M was 3.5km ahead of her.

Hence when L completed the race, M would be (2*3.5) or 7km ahead of L if M did not stop after finishing the race.

7/20 ----- 7/20h ------21mins

Add 21 mins to 10.45a.m , you’ll get 11.06am

Best wishes

[ooptimizer]

Thank you!

[tianzhu]

Hi MathIzzzFun


Good Morning.

Currently, I believe you are the only tutor offering solutions in this thread.

As a daddy, I would like to take this opportunity on Teachers’ Day to offer my heartfelt appreciation to you.

Best wishes

[TT2]

Hi… Need help on this qn. Thanks in advance.


In a shooting practice, Ben obtained the scores of 5, 7, 8 and 9 after shooting four times. The highest possible whole number score that Ben might score for each shot is not more than 10. After another three shots, ben’s average score became 8. Then he fired another three shots and his average score became 8.5. He scored a total of five 9s in all the ten shots. Find Ben’s score for each of the last three shots.

[MathIzzzFun]

tianzhu:

Hi MathIzzzFun


Good Morning.

Currently, I believe you are the only tutor offering solutions in this thread.

As a daddy, I would like to take this opportunity on Teachers’ Day to offer my heartfelt appreciation to you.

Best wishes

Thank you, tianzhu.

Have a great break!

cheers.

[MathIzzzFun]

TT2:

Hi... Need help on this qn. Thanks in advance.


In a shooting practice, Ben obtained the scores of 5, 7, 8 and 9 after shooting four times. The highest possible whole number score that Ben might score for each shot is not more than 10. After another three shots, ben's average score became 8. Then he fired another three shots and his average score became 8.5. He scored a total of five 9s in all the ten shots. Find Ben's score for each of the last three shots.

Hi

Total score for 1st 4 shots = 5 + 7 + 8 + 9 = 29
Total score for 7 shots = 7 x 8 = 56, so total score for 5th-7th shot = 56-29 = 27
Total score for 10 shots = 10 x 8.5 = 85, total score for 8th - 10th shot = 85 - 56 = 29 ---> 10,10,9 since there are a total of five 9s , so the 5th -7th are all 9s

Therefore, scores for the last three shots : 10,10,9 (in any order)