Saturday, December 18, 2010
Friday, October 22, 2010
An interesting topic and the kind of questions that you can expect in the TANCET quant section from these two topics will be rather elementary.
The AP topic has two formulae to remember.
The first one is to find the nth or the last term 'l' of an AP : l = a + (n - 1)d, where 'a' is the first term, n is the number of terms and 'd' is the common difference.
The second formula is to find the sum of first 'n' terms of an AP. Sn = (n/2)(2a + (n - 1)d)
Here is a question that tests your understanding of these concepts.
If the first term of an AP is 12 and the 7th term is 36, what is the sum of these 7 terms?
The first term a = 12
The 7th term l = 36.
We know that l = a + (n - 1)d
or 36 = 12 + (7 - 1)d
or 24 = 6d
or d = 4.
Sum of these first 7 terms = (n/2)(a + (n - 1)d), where n = 7, a = 12, d = 4
Substituting we get, (7/2)(2*12 + (7 - 1)4)
= (7/2)(24 + 24)
= 7 * 24
Choice (2) is the correct answer.
Tuesday, January 19, 2010
The concept is extremely simple : Distance = Speed * Time
The place where you need to be careful is to make sure that the units that you use for the different quantities have integrity i.e., if the unit for speed used is km/hr, then you should use hour as the unit for time.
Here is a simple question in speed time distance.
Traveling at 4/5ths of her usual speed, Sonal reached office 20 minutes late. How long did she take today?
1. 60 minutes
2. 80 minutes
3. 100 minutes
4. 64 minutes
5. 96 minutes
She travels at 4/5th of her usual speed.
Let her usual speed be 's' km/min. So, today she travels at 4/5s.
Let the usual time she takes be 't' minutes. So, today she will take (t + 20) minutes.
As the distance traveled in both the cases is the same, we can equate them
i.e., st = 4/5s (t + 20)
dividing both sides by 's' we get t = 4/5(t + 20)
or 5t = 4t + 80
or t = 80 minutes.
t is the usual time take.
The time taken today is t + 20 = 100 minutes.
Note: 1. We used km/min as the unit for speed as the unit of time given in the question is in minutes.
2. we did not stop at finding the value of 't'. The question was about finding the time taken today = t + 20.
You can get additional questions on speed time and distance at this link.
Sunday, January 10, 2010
Here is a work time question. You could expect a question on this topic. A topic that gets usually tested in the test.
A works twice as fast as B does and together they complete a task in 8 days, how long will A lone take to complete the task?
1. 16 days
2. 4 days
3. 32 days
4. 12 days
5. 24 days
Choice (4). 12 days.
A works twice as fast as B does.
So, if B does 'x' units of work in a day, then A does 2x units of work in a day or in a day they do 3x units of work.
Together, they complete the task in 8 days.
i.e., in a day together they complete 1/8th of the total task.
3x = 1/8th of the task.
So, x = 1/24th of the task.
We know A does 2x units of work a day = 2 * (1/24) = 1/12th of the work in a day.
So, A will take 12 days to complete the task.
You could access additional questions on Work Time and Pipes Cisterns here