Explanation

Explanation

The number of ways to choose 2 students from a class of 20 students is represented by the combination formula:

C(20,2) = 20! / (2! x (20-2)!)

where ! denotes the factorial function.

Simplifying the formula, we get:

C(20,2) = (20 x 19) / 2

= 190

So, there are 190 ways to choose 2 students from a class of 20 students.

Explanation

X can do the work in 20 days, so X's work rate is 1/20 of the work per day.

Y can do the work in 12 days, so Y's work rate is 1/12 of the work per day.

X works alone for 4 days, completing 4/20 = 1/5 of the work.

Y joins X, and together they complete the remaining 4/5 of the work.

Their combined work rate is (1/20 + 1/12) = 8/60 = 2/15 of the work per day.

Since they complete 4/5 of the work together, it takes them (4/5) / (2/15) = 6 days to complete the remaining work.

Adding the 4 days X worked alone, the total duration is 4 + 6 = 10 days.

So, the correct answer is: 10 days.

Explanation

Crop require water = 3 liters per square meter 

how much require for 500 square meter = 500*3

= 1500 liters 

Explanation

C

ANS:

it is to note that in a fraction, the primary term of a proportion is called antecedent and the moment term is said to be consequent. Here the proportion is 5 : 13

The predecessor is 5 and the ensuing 13

antecedent is 33

Explanation

C

ANS:

it is to note that in a fraction, the primary term of a proportion is called antecedent and the moment term is said to be consequent. Here the proportion is 6 : 7 The predecessor is 6 and the ensuing 7 predecessor is 25,

Explanation

The difference between consecutive terms of the given series are respectively 5, 7, 9, 11 and 13.

Clearly, 34 is a wrong number and must be replaced by (24 + 11) i.e. 35.

Explanation

Let total wagers = x

We know that 10% fired while 90% survived so,

90% of x = 540

90 * x = 450 

⇒      x = 600

Explanation

At 5% loss. SP =Rs.95x100$=Rs.\frac{95x}{100}$

Now,95x100+80=105x100$Now,\frac{95x}{100}+80=\frac{105x}{100}$

=>105x100−95x100=80$=>\frac{105x}{100}-\frac{95x}{100}=80$

=>105x−95x100=80$=>\frac{105x-95x}{100}=80$

=>x=800010=Rs.800

Explanation