Q&A - P5 Math

[redruby]

Dennis bought a book. He read 3/5 of the book on the first day and 1/4 of the remaining book on the second day. If Dennis read 4 pages of the book on the second day, how many pages of the book are left unread?

[redruby]

......

[magicpiglet]

Dennis bought a book. He read 3/5 of the book on the first day and 1/4 of the remaining book on the second day. If Dennis read 4 pages of the book on the second day, how many pages of the book are left unread?

Can't show pic for model as I dunno how to load pic
Bt solution ....
5/5-3/5=2/5( remaining pgs unread after 1st day)
2/5 x1/4=1/10
1 u=4 pges
5/5 -3/5-1/10=3/10
3u= 4x3
=12

[guest2013]

[guest2013]

Suggested answer:

No. of even no in group = n
Smallest even no Smallest even no = 2 + [n x (n-1)]

a) Smallest even no in group 6 will be
2 + (6 x 5) = 32

b) Smallest even no in group 45 will be
2 + (44 x 45) = 1982

c) 2 + (n x (n-1)) = 134
n x (n-1) = 132
11 x 12 = 132
Therefore group 12 will has smallest even no of 132

[guest2013]

Hi,

Here is a question which I also have the steps to solving the problem but I need clarification on one step. Kindly assist.

Mrs Lee made some cookies and packed them in 50 small boxes and 12 big boxes that had an equal number of cookies each. Each big box had 30 more cookies than each small box. 5/8 of the cookies made were packed in small boxes.
(a) Mrs Lee collected $559.90 after selling all the small boxes of cookies at $8.55 each and some big boxes of cookies at $16.50 each. How many big boxes of cookies were left?
(b) How many cookies did Mrs Lee make?

So the steps to solving (b) is as follows:

Big Small Total
3 5 8
(x10) 30 50 80

12 big boxes = 12u + (30x12)
30u = 12u + 360
18u = 360
1u = 20

Total cookies made = 80u x 20
= 1,600

Question: why do we multiply the original ratio by 10?

Many thanks in advance!

Alternative solution to (b):
Assuming:
Total cookies in 1 small box is 1 unit,
Total cookies in 1 big box will be 1 unit + 30
Total cookies in 50 small boxes = 50 units ----> (A)
Total cookies in 12 big boxes = 12 units + 360 ---> (B)

Total cookies packed in small boxes is 5 parts, ---->(C)
Total cookies packed in big boxes will be 3 parts, --> (D)

Comparing (B) and (D),
3 parts = 12 units + 360
So, 1 part = 4 units + 120

Comparing (A) and (C),
5 parts = 50 units
5 x (4 units +120) = 50 units
20 units + 600 = 50 units
30 units = 600
1 unit = 20

Total cookies made will be:
50 units + 12 units + 360
= (62 units x 20/unit) + 360
= 1600

[Oldschool]

Hi,

Here is a question which I also have the steps to solving the problem but I need clarification on one step. Kindly assist.

Mrs Lee made some cookies and packed them in 50 small boxes and 12 big boxes that had an equal number of cookies each. Each big box had 30 more cookies than each small box. 5/8 of the cookies made were packed in small boxes.
(a) Mrs Lee collected $559.90 after selling all the small boxes of cookies at $8.55 each and some big boxes of cookies at $16.50 each. How many big boxes of cookies were left?
(b) How many cookies did Mrs Lee make?

So the steps to solving (b) is as follows:

Big Small Total
3 5 8
(x10) 30 50 80

12 big boxes = 12u + (30x12)
30u = 12u + 360
18u = 360
1u = 20

Total cookies made = 80u x 20
= 1,600

Question: why do we multiply the original ratio by 10?

Many thanks in advance!

Hi,

If you considered the original ratio,

no. of cookies in one small box = 5U/50 = 0.1U



Now, if you multiply the original ratio by 10, then

no. of cookies in one small box = 50U/50 - 1U



From the subsequent workings, you could see that it is easier to work with a whole no. (in this case 1) then working with a decimal or fraction (in this case 0.1 or 1/10). Thus reducing careless mistakes in computing.

You could also multiply it with 100 but we do not want to work with a large no. either.

So long that you are comfortable and confident, be it whole no., decimal or fraction, all of them will give the same answer.

Regards

[Daddy]

Thank guest2013

[guest2013]

Thank guest2013

No problem, glad to share

[redruby]

Dennis bought a book. He read 3/5 of the book on the first day and 1/4 of the remaining book on the second day. If Dennis read 4 pages of the book on the second day, how many pages of the book are left unread?

Can't show pic for model as I dunno how to load pic
Bt solution ....
5/5-3/5=2/5( remaining pgs unread after 1st day)
2/5 x1/4=1/10
1 u=4 pges
5/5 -3/5-1/10=3/10
3u= 4x3
=12