EPRI (Economic Policy Research Institute) Interview Questions, Process, and Tips

( d ) Root

d=7s—–equation 1
d=5(s+12)
7s=5(s+12)
7s=5s+60
2s=60
s=30
from equation 1
d=7*30
d =210km

$150000

Let d = 7r. And use distance is = rate × time
7r= ( r+12) 5
7r= 5r + 60
Subtract 5r from both sides
2r = 60
Divide out 2
Rate = 30 km/h
Original question 30 km/h × 7 = 210
30 +12 = 42× 5 = 210

=> 3s = d
=> 5(s-9) = d

therefore
5s-45=3s
2s = 45
s=22.5

hence
d= 67.5

The first 10 odd prime numbers are 3, 5, 7, 11, 13, 17, 19, 23, 29 and 31.

Sum of the odd prime numbers = (3+5+7+11+13+17+19+23+29+31)

= 158

Number of odd prime numbers = 10

We know, Average = (sum of the 10 odd prime numbers ÷ Number of odd

prime numbers)

Average =

= 15.8

∴ The Average of first 10 prime numbers which are odd is 15.8

(N * 1.1) * 0.9 = 7920
N=8000

Let’s assume the length of each train is ‘L’ and the speeds of the two trains are ‘V₁’ and ‘V₂’ respectively.

When the trains are moving in the opposite direction, their relative speed is the sum of their individual speeds. The total distance they need to cover is the sum of their lengths. Since they cross each other completely in 5 seconds, we can set up the following equation:

(V₁ + V₂) × 5 = 2L

When the trains are moving in the same direction, their relative speed is the difference between their individual speeds. The total distance they need to cover is the difference between their lengths. Since they cross each other completely in 15 seconds, we can set up the following equation:

(V₁ – V₂) × 15 = 2L

Now, let’s solve these equations to find the ratio of their speeds.

From the first equation, we have:
(V₁ + V₂) × 5 = 2L
V₁ + V₂ = (2L) / 5

From the second equation, we have:
(V₁ – V₂) × 15 = 2L
V₁ – V₂ = (2L) / 15

Let’s add these two equations together:
V₁ + V₂ + V₁ – V₂ = (2L) / 5 + (2L) / 15
2V₁ = (6L + 2L) / 15
2V₁ = (8L) / 15
V₁ = (4L) / 15

So, the speed of the first train is (4L) / 15.

Now, let’s substitute this value back into the first equation to find V₂:
(4L) / 15 + V₂ = (2L) / 5
V₂ = (2L) / 5 – (4L) / 15
V₂ = (6L – 4L) / 15
V₂ = (2L) / 15

Therefore, the speed of the second train is (2L) / 15.

The ratio of their speeds is given by:
(V₁ / V₂) = ((4L) / 15) / ((2L) / 15)
(V₁ / V₂) = 4L / 2L
(V₁ / V₂) = 2

So, the ratio of their speeds is 2:1.