Please provide explanation for these GMAT PREP Questions

[DREAM GMAT]

1. A company assigns ID number to employees. Each is to consist of 4 different digits from 0 to 9 inclusive except 1st digit cannot be 0. How many different combinations are there?
a. 3024
b. 4536
c. 5040
d. 9000
e. 10000


2. Angela's grade was in the 90th percentile out of 80 grades in her class. In another class there were 19 grades higher than Angela's. If nobody had Angela's grade, then Angela was what percentile of the two classes combined?
a. 72
b. 80
c. 81
d. 85
e. 92

Regards

[mpaudena]

2. Angela's grade was in the 90th percentile out of 80 grades in her class. In another class there were 19 grades higher than Angela's. If nobody had Angela's grade, then Angela was what percentile of the two classes combined?
a. 72
b. 80
c. 81
d. 85
e. 92

Regards

I've seen question number 2 before. Are you sure that in the second class there aren't 100 grades? That is are you sure you transcribed the question correctly?

If you were accurate then I don't understand the answer and when I did this I just assumed there was 100 grades. I'm sure with that you can find the answer by adding the total number of grades, which is 180 and the totals of Angela's position (72 and 81) which is 153. The resulting percentage is 85.

[crackgmat007]

1. B

4 digits

thousands - we have 9 numbers (excluding 0)
hundreds - we have 9 numbers (now incliding 0 & excluding the number assigned for thousands)
tens - 8 numbers
units 7

HTH

[papgust]

Forgive if my question sounds stupid.

For qn #1, it mentions "find different combinations". Do we have to employ permutation formula/ combination formula?

I understand that by using permutation formula, correct answer choice will be 4536 which is part of answer choice. But the word "combinations" confuses me.

Pls help me understand.

[DREAM GMAT]

1. B

4 digits

thousands - we have 9 numbers (excluding 0)
hundreds - we have 9 numbers (now incliding 0 & excluding the number assigned for thousands)
tens - 8 numbers
units 7

HTH

thanks

I missed the term "different" n got confused.

Thanks for the Clariifcation.

[DREAM GMAT]

2. Angela's grade was in the 90th percentile out of 80 grades in her class. In another class there were 19 grades higher than Angela's. If nobody had Angela's grade, then Angela was what percentile of the two classes combined?
a. 72
b. 80
c. 81
d. 85
e. 92

Regards

I've seen question number 2 before. Are you sure that in the second class there aren't 100 grades? That is are you sure you transcribed the question correctly?

If you were accurate then I don't understand the answer and when I did this I just assumed there was 100 grades. I'm sure with that you can find the answer by adding the total number of grades, which is 180 and the totals of Angela's position (72 and 81) which is 153. The resulting percentage is 85.

Your answer is correct but i am not convinced with explanation.

Since statement states that Angela Grade is 90% tile of 80 Grade which mean she has a grade of 72.

Also statement states that another class is having highest grade which is 19 more than Angela's grade i.e. highest grade for other class will (72+19=91).

Now if we take both classes together we have a maximum grade of 91 & Angela scored 72. Now if we calculate the percentile it should be = (72/91)*100 (i.e. 79.*** %tile)

Which is not the available option.

Please clarify if i missed something.

Regards
Mandeep