# Thread: 1200 stamps problem (with suggested solution)

1. ## 1200 stamps problem (with suggested solution)

There is a collection of stamps where 68% are foreign stamps, 45% are issued more than 10 years ago and 30% are foreign stamps issued over 10 year ago.
There are 1200 stamps in total.

How many foreign stamps issued within 10 years?

My solution is (look at the image below):

Attachment 19830

68% of 1200 = 816 which is the total number of Foreign stamps
45% of 1200 = 540 which is the total of 10+ stamps. Therefore 660 are total of foreign stamps issued 10- years.
30% of 660 = 198 which is the foreign stamps issued 10- years.

2. You are given that "45% of the stamps were issued more than 10 years ago". You are assuming that that same percentage applies to both domestic and foreign stamps. What right do you have to make that assumption?

3. I can't solve better than that. any suggestion? so you're saying that the question is incomplete or what?

4. Hello, Narek!

There is a collection of 1200 stamps.
68% are foreign stamps.
45% are issued more than 10 years ago . (This is irrelevant.)
and 30% are foreign stamps issued over 10 year ago ("old").

How many foreign stamps issued within 10 years ("new")?

There are: .$\displaystyle 68\% \times 1200 \:=\:816$ foreign stamps.

There are: .$\displaystyle 30\% \times 1200 \:=\:360$ foreign stamps which are old.

Therefore, there are: .$\displaystyle 816 - 360 \:=\:456$ foreign stamps which are new.

5. no, I don't think this is correct. 45% of all the stamps are issued more thant 10 years ago. Therefore, 55% are issued within 10 years.

6. Hello, Narek!

There is a collection of 1200 stamps.
68% are foreign stamps,
45% are issued more than 10 years ago ("old")
30% are foreign stamps issued over 10 year ago.

How many foreign stamps issued within 10 years ("new")?

Place the information in a chart . . .

. . $\displaystyle \begin{array}{c||c|c||c|} & \text{Old} & \text{New} & \text{Total} \\ \hline\hline \text{Foreign} & {\bf30\%} & & {\bf68\%} \\ \hline \text{U.S.} & & & & \hline\hline \text{Total} & {\bf45\%} & & 100\% \\ \hline \end{array}$

Complete the chart:

. . $\displaystyle \begin{array}{c||c|c||c|} & \text{Old} & \text{New} & \text{Total} \\ \hline\hline \text{Foreign} & 30\% & {\bf38\%} & 68\% \\ \hline \text{U.S.} & {\bf15\%} & {\bf17\%} & {\bf32\%} \\ \hline\hline \text{Total} & 45\% & {\bf55\%} & 100\% \\ \hline \end{array}$

The question is "How many stamps are foreign and new?"

Answer: .$\displaystyle \text{38\% of 1200}$

7. Code:
        Number     > 10 years
Foreign 816 (68%)  244.8 (30% of 816)
Local   384 (32%)  295.2 (540 - 244.8)
====        =====
Total  1200        540.0 (45% of 1200)

8. Thank you folks for the answers but as you see we have 3 different answers here! 3 different approaches, excluding mine! Which one do you think is the correct answer?

9. Originally Posted by Narek
Thank you folks for the answers but as you see we have 3 different answers here! 3 different approaches, excluding mine! Which one do you think is the correct answer?
Well, show all 4 solutions to your teacher: it'll prove how unclear he/she is!!

For the record: I'm sure that Soroban's answer of 456 is what's intended.

There are 816 (1200 * .62) F-stamps
There are 360 (1200 * .30) F-stamps > 10y
There are 456 (816 - 360) F-stamps =< 10y

Problem should be clarified, like:
A collection contains 1200 stamps.
68% of the collection are Foreign stamps.
30% of the collection are Foreign stamps > 10 years.
How many Foreign stamps are =< 10 years ?