# Lecture-7

00:03:44 NCERT Exercise 5.3 Question 8 Find the sum of first 51 terms of an AP whose second and third terms are 14 and 18 respectively.

00:06:34 NCERT Exercise 5.3 Question 9 If the sum of first 7 terms of an AP is 49 and that of 17 terms is 289, find the sum of first n terms.

00:13:14 NCERT Exercise 5.3 Question 10

00:24:04 NCERT Exercise 5.3 Question 11 If the sum of the first n terms of an AP is 4n-n^2, what is the first term (that is S1)? What is the sum of first two terms? What is the second term? Similarly, find the 3rd, the 10th and the nth terms.

00:31:24 NCERT Exercise 5.3 Question 12 Find the sum of the first 40 positive integers divisible by 6.

00:34:14 NCERT Exercise 5.3 Question 13 Find the sum of the first 15 multiples of 8.

00:35:54 NCERT Exercise 5.3 Question 14 Find the sum of the odd numbers between 0 and 50.

00:38:54 NCERT Exercise 5.3 Question 15 A contract on construction job specifies a penalty for delay of completion beyond a certain date as follows: ₹ 200 for the first day, ₹ 250 for the second day, ₹ 300 for the third day, etc., the penalty for each succeeding day being ₹ 50 more than for the preceding day. How much money the contractor has to pay as penalty, if he has delayed the work by 30 days?

00:43:42 NCERT Exercise 5.3 Question 16 A sum of ₹ 700 is to be used to give seven cash prizes to students of a school for their overall academic performance. If each prize is ₹ 20 less than its preceding prize, find the value of each of the prizes.