Q&A - PSLE Math

[tianzhu]

shruthi:

R and D had $1250 altogether.After R spent 80% and D spent 40%,D had twice as much money left as R.Find the amount of money D had in the end.

Hi

You may use MD.

Start with D in the end.

D
Left ----- 6 units (60%)
Spent ----- 4 units (40%)

R
Left ------ 3 units (20%) ----- D had twice as much money left as R.
Spent ------ 12 units (80%)

25 units ------ 1250
1 unit ------ 50

In the end, D ------ 6 units ------ 6*50 ------ 300

Best wishes

[tianzhu]

shruthi:

J takes 6 hours to paint a house.If D helps him,they would take 4 hours.How long will D take to paint the house himself?

Hi

One way to solve it.

In 1h, J paints 1/6 of a house.

In 1h, J and D paint 1/4 of a house.

1/4 – 1/6 ------ 1/12

In 1h, D paints 1/12 of a house.

Hence, he takes 12h to paint the house himself.

Best wishes

[tianzhu]

shruthi:

J and E each have some marbles.If J gives 36 marbles to E,both of them will have the same number of marbles.If E gives 12 marbles to J,the number of marbles that J has to the number of marbles E has will be in the ratio 5:1.How many marbles does each girl have?

Hi

You may use MD or UM to solve this question.

Case 1
J ------ 1 unit x 6 ------- 6 units
E ------ 1 unit x 6 ------- 6 units

Case 2
J ------ 5 units x 2 ------- 10 units
E ------ 1 unit x 2 -------- 2 units

The total amount of money remains the same. Adjust the ratios by making the total number of units the same. Find a common multiple for 2 and 6.

4 units ------ 48
1 unit ------ 12

Total ------ 12 units ------144

J ------ 6units + 36 -------108

E ------ 144 -108 ------ 36

Best wishes

[ozora]

Can any one answer this question? It came out in the PSLE. 1)Sally has a book that contains 525 pages.Everyday from Monday to Thursday she reads 15 pages and everyday from Friday to Sunday she reads 30 pages.What is the least number of days she needs to finish reading the whole book?

[ganchiong]

ozora:

Can any one answer this question? It came out in the PSLE. 1)Sally has a book that contains 525 pages.Everyday from Monday to Thursday she reads 15 pages and everyday from Friday to Sunday she reads 30 pages.What is gee least number of days she needs to finish reading the whole book?

Ans. 24 days

[ozora]

ganchiong:

ozora:

Can any one answer this question? It came out in the PSLE. 1)Sally has a book that contains 525 pages.Everyday from Monday to Thursday she reads 15 pages and everyday from Friday to Sunday she reads 30 pages.What is gee least number of days she needs to finish reading the whole book?

Ans. 24 days

May I know how u derive it?.Thanks

[ganchiong]

ozora:

ganchiong:

[quote=\"ozora\"]Can any one answer this question? It came out in the PSLE. 1)Sally has a book that contains 525 pages.Everyday from Monday to Thursday she reads 15 pages and everyday from Friday to Sunday she reads 30 pages.What is gee least number of days she needs to finish reading the whole book?

Ans. 24 days

May I know how u derive it? Thanks[/quote]1 week you can finish 150 pages.
To complete 525 pages req 3 weeks plus...(75 pages more to go)
If you read this 75 pages during the week-end (Fri to Sun) will give you the least no of days (3).
Therefore, 21+3 = 24 days

[ozora]

Ans. 24 days[/quote]

May I know how u derive it? Thanks[/quote]

1 week you can finish 150 pages.
To complete 525 pages req 3 weeks plus…(75 pages more to go)
If you read this 75 pages during the week-end (Fri to Sun) will give you the least no of days (3).
Therefore, 21+3 = 24 days[/quote]

thanks I got 26 days assuming the by mon tues wed and thurs… hiaz… is tricky question… no wonder my nephew got stuck.
thanks

[daranic]

Qn appears in today’s Maths paper 2:


Alex and Bob were racing around a 400m track. Alex ran at a speed of 190m/min. Bob ran at a speed 25m/min lesser than Alex. How many complete rounds must Alex run to run 300m more than Bob?

[chrisu]

If can selectively choose weekend to read, then why not 525/30 = 17.5. Thus the least no. of days would become 18 days which is not among the mcq answers. I think the answer should be 26days.