Q&A - P5 Math

[elisammom]

Thanks! I got it;)

[elisammom]

Another question, pls help


There were 44 pupils in a class. 34 pupils passed science and 36 pupils passed english. 4 pupils did not pass both subject. How many pupils passed both subjects?
Ans is 30.

Tia

[Suz855]

elisammom:

Another question, pls help


There were 44 pupils in a class. 34 pupils passed science and 36 pupils passed english. 4 pupils did not pass both subject. How many pupils passed both subjects?
Ans is 30.

Tia

34+36+4=74
There are only 44 pupils in the class, thus the extra must due to pupil passing both, so

74-44=30

[elisammom]

Thanks so much!

[doraemo]

MathIzzzFun:

doraemo:

Help Needed..


120 boys are standing in front of their lockers, numbered from 1 to 120. At the start, all lockers are opened. A teacher calls out ‘1’, and since 1 is a divisor of all the numbers, all the boys close their lockers. The teacher then calls out ‘2’ , and only those boys whose locker numbers are divisible by 2 will open their lockers. The teacher then calls out ‘3’ . Those boys whose locker numbers are divisible by 3 will open their lockers if they are closed, or close their lockers if they are opened. This process is continued until ‘120’ is called out. How many lockers will be closed at the end of the entire process?

may I know the source of the question - school practice question or MO question ?

10 lockers will be closed.

cheers.

Hi MathIzzzFun
Thank you for your help. MO question.
10 lockers will be closed?

[tianzhu]

doraemo:

10 lockers will be closed?

Hi

Try to break down the question into a block of 10 lockers to establish a pattern.

You will see that the lockers that will be closed have numbers that are perfect squares and less than 120.

The locker numbers are 1,4,9,16,25,36,49,64,81,100.

Hence there are 10 lockers

Best wishes

[MathIzzzFun]

doraemo:

MathIzzzFun:

[quote=\"doraemo\"]Help Needed..


120 boys are standing in front of their lockers, numbered from 1 to 120. At the start, all lockers are opened. A teacher calls out ‘1’, and since 1 is a divisor of all the numbers, all the boys close their lockers. The teacher then calls out ‘2’ , and only those boys whose locker numbers are divisible by 2 will open their lockers. The teacher then calls out ‘3’ . Those boys whose locker numbers are divisible by 3 will open their lockers if they are closed, or close their lockers if they are opened. This process is continued until ‘120’ is called out. How many lockers will be closed at the end of the entire process?

may I know the source of the question - school practice question or MO question ?

10 lockers will be closed.

cheers.

Hi MathIzzzFun
Thank you for your help. MO question.
10 lockers will be closed?[/quote]Yes, 10 lockers (with locker numbers that are square numbers) will be closed.

Since every locker is opened at first, it will stay open if it is opened/closed EVEN number of times, and it will be closed if it opened/closed ODD number of times. Every locker will only be opened/closed when the number called is A FACTOR of the locker number.

ONLY square numbers have odd number of factors (as one of the factor has a twin), all others have even number of factors. So, only locker number which is a square will be closed odd number of times --> closed in the end.

cheers.

[panic_mum]

Hi I need help on these questions …i have been cracking my brains …Thank q…

1) There are a total of 1430 red, blue, green and yellow marbles in a box. John discovers that if he does all of the following :-
.doubles the number of red marbles;
.adds 40 blue marbles;
.removes 30 green marbles and
.removers half the yellow marble
he would get the same number of marbles for each colour.
How many green marbles are there in the box?

[Jamesbond]

Using 3/5 of her money, Chloe could buy 11 notebooks. If she was given an extra $2, she could use it together with the remaining amount of money to buy another 8 such notebooks. How much money did Chloe have?

[tianzhu]

Jamesbond:

Using 3/5 of her money, Chloe could buy 11 notebooks. If she was given an extra $2, she could use it together with the remaining amount of money to buy another 8 such notebooks. How much money did Chloe have?

Hi

3 units ------ 11NB

2 units + 2 ------ 8NB

Make the number of NB equal

24 units ------- 88NB

22 units + 22 ------- 88NB

24 units ------- 22 units + 22

1 unit ------- 11

Chloe --------- 5*11 ------ 55

Best wishes