In conditional sentences, there is an 'if clause' and a 'main clause'.  The structure of the if clause and the main clause are as given below in the three different conditionals

First Conditional or Probable Condition

If + present            -    will / shall etc. + infinitive

If you work hard, you will succeed.

This sentence refers to the future and the action mentioned in the main clause is likely to happen.

Second Conditional or Improbable Condition

If + past                -    would / should etc. + infinitive

If you worked hard, you would succeed.

This is an imaginary situation and the action mentioned in the main clause is not likely to happen.

Third Conditional or Impossible Condition

If + past perfect    -    would / should etc. + have + past participle

If you had worked hard, you would have succeeded.

This refers to the past action which did not happen.


In the higher secondary examinations there are two types of questions related to this grammar topic.  One is to fill in the blanks with the correct usage.  The other is to correct a sentence given with a wrong combination of if clause and main clause.

For example, this is from March 2020 examination:

Use appropriate forms of the words given in the brackets to fill in the blanks.

1. Hawking commented in his customary style, 'If I _____ (get) a first, I shall go to Cambridge.

2.  Ivan Ivanich said to his brother, "If I were young, I _____ follow my dreams as you did."

In the first question the main clause (I shall go to Cambridge) is as in the first conditional.  So the conditional clause should use the present tense. The present form of 'get' is 'get'.  So the answer is 'get'.

In the second question the conditional clause is having if + past (were).  So it is second conditional or type 2 conditional.  So the main clause should have would + infinitive.  So the answer is  'would follow'


Correct the following sentences:

1.  If I won a lottery, I would have bought a car.

Ans:  You can correct it in two ways.

a)  If I had won a lottery, I would have bought a car.

b)  If I won a lottery, I would buy a car.


2.  If it rains, we would cancel the trip.

Ans:

a)  If it rains, we will cancel the trip.

b)  If it rained we would cancel the trip.


Also remember that the main clause can come first and the if clause second as in,

I would buy a new bike if my parents allowed me.


Exercise:

Fill the blanks

1.  If you come at 10 o'clock, you _____ (can, could, could have ) meet/met him.

2.  If she _____ (inform) the teacher, she would not have got into so much trouble.

3.  If you _____ (speak) louder, we would understand you.

4.  You would have got wet, if it _____ (rain).

5.  If I _____ (study) hard, I will get first class.


Correct the following sentences

1.  If we start now, we would be able to finish the work by 4 o'clock.

2.  You would have got a vaccine slot if you try at 3 pm.

3.  If I had known about the exam, I would pay more attention in class.

4.  If I were the prime minister, I will uplift the poor.

5.  I would listen to you if you practice what you preached.