Part II — Short Answer Questions 18 × 2 = 36
Answer briefly. (Answer all questions.)
7.In a school, students thought of planting trees in and around the school to reduce air pollution. It was decided that the number of trees, that each section of each class will plant, will be the same as the class, in which they are studying, e.g., a section of Class I will plant 1 tree, a section of Class II will plant 2 trees and so on till Class XII. There are three sections of each class. How many trees will be planted by the students?[2]
8.Find the coordinates of the points which divide the line segment joining A(- 2, 2) and B(2, 8) into four equal parts.[2]
9.The following data gives the distribution of total monthly household expenditure of 200 families of a village. Find the modal monthly expenditure of the families. Also, find the mean monthly expenditure : Expenditure (in ₹): 1000 - 1500, 1500 - 2000, 2000 - 2500, 2500 - 3000, 3000 - 3500, 3500 - 4000, 4000 - 4500, 4500 - 5000 Number of families: 24, 40, 33, 28, 30, 22, 16, 7[2]
10.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.[2]
11.12 defective pens are accidentally mixed with 132 good ones. It is not possible to just look at a pen and tell whether or not it is defective. One pen is taken out at random from this lot. Determine the probability that the pen taken out is a good one.[2]
12.A spherical glass vessel has a cylindrical neck 8 cm long, 2 cm in diameter; the diameter of the spherical part is 8.5 cm. By measuring the amount of water it holds, a child finds its volume to be 345 cm $^3$ . Check whether she is correct, taking the above as the inside measurements, and $\pi = 3.14$ .[2]
13.A lot consists of 144 ball pens of which 20 are defective and the others are good. Nuri will buy a pen if it is good, but will not buy if it is defective. The shopkeeper draws one pen at random and gives it to her. What is the probability that (i) She will buy it ? (ii) She will not buy it ?[2]
14.If (1, 2), (4, y), (x, 6) and (3, 5) are the vertices of a parallelogram taken in order, find x and y.[2]
15.The first term of an AP is 5, the last term is 45 and the sum is 400. Find the number of terms and the common difference.[2]
16.In a classroom, 4 friends are seated at the points A, B, C and D as shown in Fig. 7.8. Champa and Chameli walk into the class and after observing for a few minutes Champa asks Chameli, “Don’t you think ABCD is a square?” Chameli disagrees. Using distance formula, find which of them is correct. In Fig. 7.8, A(3, 4), B(6, 7), C(9, 4) and D(6, 1).[2]
17.Thirty women were examined in a hospital by a doctor and the number of heartbeats per minute were recorded and summarised as follows. Find the mean heartbeats per minute for these women, choosing a suitable method. Number of heartbeats per minute: 65 - 68, 68 - 71, 71 - 74, 74 - 77, 77 - 80, 80 - 83, 83 - 86 Number of women: 2, 4, 3, 8, 7, 4, 2[2]
18.Name the type of quadrilateral formed, if any, by the following points, and give reasons for your answer: (i) (- 1, - 2), (1, 0), (- 1, 2), (- 3, 0) (ii) (-3, 5), (3, 1), (0, 3), (-1, - 4) (iii) (4, 5), (7, 6), (4, 3), (1, 2)[2]
19.Prove that the following are irrational: (i) $\dfrac{1}{\sqrt{2}}$ (ii) $7\sqrt{5}$ (iii) $6 + \sqrt{2}$[2]
20.Find the distance between the following pairs of points : (i) (2, 3), (4, 1) (ii) (- 5, 7), (- 1, 3) (iii) (a, b), (- a, - b)[2]
21.The following table gives the literacy rate (in percentage) of 35 cities. Find the mean literacy rate. Literacy rate (in %): 45 - 55, 55 - 65, 65 - 75, 75 - 85, 85 - 95 Number of cities: 3, 10, 11, 8, 3[2]
22.200 logs are stacked in the following manner: 20 logs in the bottom row, 19 in the next row, 18 in the row next to it and so on (see Fig. 5.5). In how many rows are the 200 logs placed and how many logs are in the top row?[2]
23.If the 3rd and the 9th terms of an AP are 4 and - 8 respectively, which term of this AP is zero?[2]
24.A die is thrown once. Find the probability of getting (i) a prime number; (ii) a number lying between 2 and 6; (iii) an odd number.[2]