Q&A - PSLE Math

[tianzhu]

Hi, lizawa

Thanks for your help.

[tianzhu]

Q1) Alan had some apples. When he packed them into bags of seven apples, he would have 3 apples left. When he packed them into bags of nine apples, he would be short of 6 apples. What was the least number of apples that Alan had?


This problem may be solved by listing and Guess and Check which are tedious.

Wish to seek help from members who may be aware of any more effective method.

[corneyAmber]

is this ok?


10+ (7* ?) = 10 + 78 = 66

3 + (9 ?) = 3 + 9*7 = 66

if kids know their times table well, this is fast.

[tianzhu]

ks2me:

is this ok?


10+ (7* ?) = 10 + 7*8 = 66

3 + (9* ?) = 3 + 9*7 = 66

if kids know their times table well, this is fast.

Hi ks2me

Please elabrate more, why 10+, ......?

[corneyAmber]

pardon me if my brain thinks too simply...



i used the first sequence as (7+3) + 7 + 7 + 7........... so 10 + (7*?)

and second as (9-6) + 9 + 9 + 9 .................. so 3 + (9*?)

10 + (7*?) = 3 + (9*?)

7 + (7* ?) = 9*?

can do?

[suiyuan]

Thank you for your help.



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[lizawa]

Let AD be x cm

Let AB be y cm
\t
Perimeter of ABCD = 20cm
so, x+y = 20/2 = 10 cm

Area of big square = y2
Area of small square = x2

Area of 4 sqaures = 80 square cm
So area of 1 big + 1 small = 40 square cm

x2 + y2 = 40

x + y = 10
(x+y)(x+y) = 100
x2 + y2 + 2xy = 100
40 + 2xy = 100
2xy = 60
xy = 30

Area of shaded rectangle = xy = 30 square cm.

Is the answer correct ?

[suiyuan]

Hi lizawa


Thank You.
I am sorry, no answer was given.

[suiyuan]

Thank You for your time.


1) Kenneth wants to rent a bicycle from Jim’s Bicycle Kiosk. The cost of renting a bicycle for d hours is given by C = $(3d + 5). Find the cost of renting the bicycle if Kenneth wants to cycle for 4 hours. (2 marks)


2) After 20 minutes in a cross-country race, Alan has run 5/8 of the route while Bernard has covered only 3/8 of the distance. Both run at a uniform average speed each and Bernard runs 60m/min slower than Alan.
(a) Find the total distance of the race.
(b) If Bernard wants to finish at the same time as Alan, by how much should he increase his average speed for the remainder of the race? Express the answer in m/min
(5 marks)

[ChiefKiasu]

lizawa:

...

(x+y)(x+y) = 100
x2 + y2 + 2xy = 100
40 + 2xy = 100
2xy = 60
xy = 30

Area of shaded rectangle = xy = 30 square cm.

Is the answer correct ?

*clap* *clap* That is the right answer. However, are children in P6 taught how to do an expansion of (x+y)^2 ? Without that step, it is impossible to solve the equation.