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National Education => Admissions tests => Selective Schools Admissions Tests => Topic started by: academiic on December 01, 2018, 02:26:45 pm

Title: Numerical Reasoning Help!!
Post by: academiic on December 01, 2018, 02:26:45 pm
A van leaves a house travelling at an average rate of 35 km/h. The family leaves the house 3/4 hour later following the same route in a car. They travel at an average rate of 50 km/h. How long after the van leaves the house will the car catch up with the van?

A: 2 hours B: 2 hours 15 minutes C: 2 hours 30 minutes D: 2 hours 45 minutes E: none of these

Thanks!
Title: Re: Numerical Reasoning Help!!
Post by: Chelsea f.c. on December 01, 2018, 02:45:34 pm
The van gets a head start and travels 35×.75km=26.25km in 3/4hrs so solve 35x+26.25=50x to get 1.75 hrs
Title: Re: Numerical Reasoning Help!!
Post by: academiic on December 01, 2018, 03:13:41 pm
Quote from: Chelsea f.c. on December 01, 2018, 02:45:34 pm
The van gets a head start and travels 35×.75km=26.25km in 3/4hrs so solve 35x+26.25=50x to get 1.75 hrs

I checked the answer and it is 2 hours and 30 minutes... still don't know how tho? thx
Title: Re: Numerical Reasoning Help!!
Post by: AlphaZero on December 01, 2018, 03:37:47 pm

The answer is 2 hours and 30 minutes :)
Title: Re: Numerical Reasoning Help!!
Post by: academiic on December 07, 2018, 11:40:25 pm
Thank you for that explanation.
Title: Re: Numerical Reasoning Help!!
Post by: academiic on December 12, 2018, 07:10:46 pm
Hi guys I have a new question

the sum of three student's marks is 164. the first student got 12 marks more than the third student. the second student had two times the mark of the first student. How many marks did the third student get?

Title: Re: Numerical Reasoning Help!!
Post by: TheAspiringDoc on December 12, 2018, 07:14:51 pm
Spoiler
Have you really tried it by yourself?  :P
If yes, then open the spoiler below :)
If no, you're only cheating yourself!!!!  :o
Spoiler
Let 'third student' = m
first student = m + 12
second student = 2(m +12)

Therefore m + [m+12] + [2(m+12)] = 164.
4m + 36 = 164
4m = 128
m = 32
The third student got 32 marks (RIP)
^^ that's the answer but look at Lear's post and have a go by yourself first  ;)
Title: Numerical Reasoning Help!!
Post by: Lear on December 12, 2018, 07:15:57 pm
Hey!
Let me help you along.
So when I approach this question I note that
- The score of the second student is dependent on the score of the first student
- The score of the first student is dependent on the score of the third student
- We don’t know the score of the third student and it is independent of the other students


So I’d go ahead and let the score of the third student be x
Then I would express the scores of the other two students in terms of the score of the third student (x) and then add these all up and solve for 164.

Give it a shot and let us know if you need more help!

***Beaten above but I will leave this here so one can understand how to approach such questions.
Title: Re: Numerical Reasoning Help!!
Post by: academiic on January 03, 2019, 06:28:42 pm
Quote from: Lear on December 12, 2018, 07:15:57 pm
Hey!
Let me help you along.
So when I approach this question I note that
- The score of the second student is dependent on the score of the first student
- The score of the first student is dependent on the score of the third student
- We don’t know the score of the third student and it is independent of the other students


So I’d go ahead and let the score of the third student be x
Then I would express the scores of the other two students in terms of the score of the third student (x) and then add these all up and solve for 164.

Give it a shot and let us know if you need more help!

***Beaten above but I will leave this here so one can understand how to approach such questions.

Hello!! your explanation really helped me when approaching such questions especially since maths is my weakness. thank you very much!
Title: Re: Numerical Reasoning Help!!
Post by: academiic on January 21, 2019, 06:44:45 pm
New question:
 Iris was absent to an exam because of a fever, so she had to take her Maths test a few days
late. She scored 96 on her exam which was found to raise the class average on the test from 81
to 82. How many students took the test altogether?
A. 12 B. 13 C. 14 D. 15 E. None of these
Title: Re: Numerical Reasoning Help!!
Post by: fun_jirachi on January 21, 2019, 07:03:14 pm
Let the number of students without Iris be n. Then, their total score without her score of 96 becomes 81n. With her included, the number of students is n+1, and the class average is 82. Then the total score becomes 82(n+1). The difference between those is her score of 96 is included in the latter but not the former. Simple algebra should allow you to solve for n.

Hope this helps :)