Q&A - PSLE Math

[marstolive]

Thank u guest2013

[htn]

please help.

At 11.00 a.m. Justin drove from Town S to Town T at an average speed of 70km/h. At the same time, Terry set off from Town T towards Town S. Some time later, they passed each other and were 10 km apart at 2 p.m. Justin arrived at Town T at 4 p.m.

a) Find the average speed of Terry.
b) Find the time at which Terry arrived at Town S.

TIA

From 2 p.m. to 4 p.m. ---> 2 h

70 x 2 = 140 km

From 11 a.m. to 2 p.m. ---> 3 h

140 + 10 = 150 km

150/3 = 50 km/h (ans a)

70 x 5 = 350 km

350/50 = 7 h

7 h after 11 a.m. ---> 6 p.m. (ans b)

Thank you.

[alfretztay]

Ali is 30 yrs old now. His father is 65 years. How many years ago was his father 5 times as old as him?

Hi,

Please check the numbers again.
.

I would solve the question as follows :

30 - 1u = 65 - 5u
4u -> 35
1u -> 8.75
30 - 8.75 = 21.25
Ans : 21.25 years

Alternatively,
5u -> 43.75
65 - 43.75 = 21.25.
Ans : 21.25 years

[Leewk]

Please help.

A bus can have a maximum of 42 children or 36 adults.
Given that there are already 28 children and 8 adults in the bus, what is the greatest numbers of adults that can board the bus ?

The answer is '4' but I don't have the solution.

[guest2013]

Please help.

A bus can have a maximum of 42 children or 36 adults.
Given that there are already 28 children and 8 adults in the bus, what is the greatest numbers of adults that can board the bus ?

The answer is '4' but I don't have the solution.

42 C is equiv. to 36 A
14 C is equiv. to 12 A

Max 42 C, already 28 C in the bus, remaining capacity is 14 C or 12A
As there are 8 A in the bus, the bus can take 4 more adults

[Leewk]

[quote="guest2013"][quote="Leewk"]Please help.

A bus can have a maximum of 42 children or 36 adults.
Given that there are already 28 children and 8 adults in the bus, what is the greatest numbers of adults that can board the bus ?

The answer is '4' but I don't have the solution.[/quote]

42 C is equiv. to 36 A
14 C is equiv. to 12 A

Max 42 C, already 28 C in the bus, remaining capacity is 14 C or 12A
As there are 8 A in the bus, the bus can take [b]4 [/b]more adults[/quote]

Thank you ! but y u times 3, can u explain more.

[MrKiasuAllTheWay]

A bus can have a maximum of 42 children or 36 adults.
Given that there are already 28 children and 8 adults in the bus, what is the greatest numbers of adults that can board the bus ?

To solve the question, we have to understand that the 'mass' (which is unstated) is the same for the 42 children and 36 adults. We can then solve the question using the unitary method.

42u=36p
7u=6p

In place of 7 children can be six adults. So, 28 divided by 7u is 4. 4 multiplied by 6 is 24(the exchange of the 28 children for adults). 36 adults is the maximum capacity of the bus. So, we shall take 36-24-8=4(The answer)

Hope my explanation was detailed enough.

[vsk]

Hi,

Is there a simple way of doing this question as it is a 1 mark question ?

Arrange the following fractions from the smallest to the largest:

4/5, 5/6, 9/11, 11/13

(Rosyth Prelim - 2014 Paper 1)

Thanks

[Kangkangteo]

Hi,

Is there a simple way of doing this question as it is a 1 mark question ?

Arrange the following fractions from the smallest to the largest:

4/5, 5/6, 9/11, 11/13

(Rosyth Prelim - 2014 Paper 1)

Thanks

8/10, 10/12, 9/11, 11/13

8/10, 9/11, 10/12, 11/13

4/5, 9/11, 5/6, 11/13 (ans)

[Kangkangteo]

Please help.

A bus can have a maximum of 42 children or 36 adults.
Given that there are already 28 children and 8 adults in the bus, what is the greatest numbers of adults that can board the bus ?

The answer is '4' but I don't have the solution.

42 C ---> 36 A

28 C ---> 36/42 x 28 = 24 A

28 C + 8 A ---> 24 A + 8 A = 32 A

36 A - 32 A = 4 A (ans)