GRE Exam Numerical Ability Time and Work

A and B can do a piece of work in 24 days, B and C can do it in 30 days and C and A can do it in 40 days. Which of the following statements is true? Indicate all correct options.
A. A takes 40 days to do the work
B. B takes 40 days to do the work
C. C takes 120 days to do the work
D. B takes 120 days to do the work
E. C takes 60 days to do the work

Read Solution (Total 1)

A+B=24; B+C=30;C+A=40 this is step 1;
Take lcm of 24,30,40 is 120;
a+b=120/24=5;b+c=120/30=4;c+a=120/40=3;
combine all the equations in step 1 to get
2(a+b+c)=12;
substitute a+b=5;
2(5+c)=12;c=1;
c alone work =total work/by c unit work;
here unit work of c is 1;
therefore c alone work=120/1=120;
do rest all the options .Hope it helps you
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GRE Other Question

Let A = {-1, 0, 2, 3, 5, 6} and f(x) = x^2 -x -2. Find f(A). Indicate all correct options. [x^2 = x*x]
A. {-1, 0, 2, 3, 5, 6}
B. {f(-1), f(0), f(2), f(3), f(5), f(6)}
C. {-2, 4, 18, 28}
D. {0, -2, 4, 18, 28}
E. { 0, 1, 2, 6, 20} A shopkeeper marks his goods at 20% profit and gives a discount of 5%. Which of the following is/are true?
A. He gained 15%
B. He suffered a loss in the transaction
C. He gained 14%
D. If the cost price was Rs.200, the selling price after the discount was Rs. 228