Question 76. Find the value of K for which the points (2,5), (K,11/2), (4,6) are collinear by Ganesh RJ, answered on Oct 7, 2007 at 8:59 p.m.
Answer 76.  Let A(2,5), B(K,11/2) and C(4,6)
                Since the points are colliniear
                therefore area of triangle ABC = 0
                1/2[2(11/2 - 6) + k(6 - 5) + 4(5 - 11/2)] = 0
        or      2(-1/2) + k(1) + 4(-1/2) = 0
        or       - 1 + k - 2 = 0
        or        k = 3
Question 77. Prove the identity (1+sinA-cosA)/(-1+sinA+cosA) = (cosecA+1)/(cosecA-1) by Naveen Kumar, answered on Oct8, 2007 at                   8:54 p.m.
Answer 77. Download answer
Question 78. A farmer has 49 cows.Each cow gives the same amount of milk(in kgs) as its no.For example 1st cow gives 1kg milk,2nd cow gives 2 kgs.......................49th cow gives 49kgs.These cows are to be distributed to 7 persons such that each gets 7 cows & each one should get equal amount of milk. Also describe which person gets which no. of cows? by Mohit Khetpal, answered on Oct 11, 2007 at 8:55 p.m.
Answer78. 1,2,3,4 ........49
               this forms an A.P. with first term(a) = 1, and common difference (d) = 1
               Total milk given by all cows = (n/2)(a + l) where l is the last term
                                                    =  (49/2)(1 + 49)
                                                    =  (49/2)50
                                                    =  1225 kg
              Each of the 7 persons gets  =  1225/7
                                                    =  175 kg of milk giving cows.
Though the last part is not in syllabus but still we answer it the possibilities may be
first person        1,2,3,25,47,48,49
Second person   4,5,6,26,43,45,46
Third person      7,8,9,24,41,42,44
Fourth person    10,11,12,27,36,39,40
Fifth person       13,14,15,23,35,37,38
Sixth person      16,17,18,28,29,33,34
Seventh person  19,20,21,22,30,31,32

Question 79. The angles of elevation of the top of tower  from two points P and Q  at distances of a and b from the base and in the same straight line with it are  complementary prove that the height of tower is (ab)^1\2. by Kavita, answered on Oct 12, 2007 on 9:01 p.m.
Answer 79. Download Answer
Question 80. Please send me urgently the answer to the following question : In a condition when the ratio of corresponding sides of two triangles are equal,are the numerator and denominator of these sides equal too? by Deepanshu Kaushal, answered on Oct 13, 2007 at 9:44 p.m.
Answer 80. No. example - In Triangle ABC, AB = 5cm, BC = 6cm, CA = 7 cm and In Triangle PQR, PQ = 10cm, QR = 12cm, RP =  14cm.
Now  AB/PQ =  BC/QR =  CA/RP  =  1/2, but AB and PQ, BC and QR, CA and RP are not equal.

Question 81.Plz solve this.If the poly.x^4 –6x^3 + 16x^2 –25x +10 is divided by x^2- 2x + k..the remainder comes out to be x + a, find k and a. by Shishira, answered on Oct 18, 2007 at 10:24 pm I.S.T.
Answer 81. Download answer
Question 82. If a hemi sphere is cut from a side of a cube the surface area increases or decreases. by sanjay, answered on oct 23 at 7:59 p.m. I.S.T.
Answer 82. The area increases as the decrease in area is pie r×r and increase in area is 2pie r×r
Question 83. One root of Quadratic polynomial is squareroot5. Find the quadratic polynomial. By Ankit Gupta, Answered on Oct 27 at 11:45 p.m. I.S.T.
Answer83. The other root is - squareroot5. The required polynomial is (x-squareroot5)(x+squareroot5) =  x^2 - 5
Question 84. When I draw graph of equations x - y = 10 and 2x - 3y = - 40 I get nearly parallel lines but answer given in book is that lines are consistent. by Rakesh, answered on Oct 28, 2007 at 5:48 p.m. 
Answer 84. You have to use an appropriate scale in such  cases . In this use 1cm = 10 units the lines intersect at x = 70, y=60
Question 85. Sir I want to know what type of questions of 1 mark each comes in Board X class examinations, Akhil Mittal at Oct 29 2007 at 7:46Pm  I.S.T.
Answer 85. For answer to a question download the three model sample paper issued by CBSE for march 2008 exams. These can be downloaded from over board downloads page go to the download page.
Question 86. I have already downloaded and solved the three official model sample papers. From where can i get more one mark questions for class x in maths. By Shivam Answered on Oct 31at 10:00 p.m. I.S.T.
Answer 86. Our chapter wise sample papers contain one mark questions which can be downloaded from here
Question 87. Monthly wages of 10 employees of a factory are (all in Rs.) 3000, 3500, 3800, 3200, 3600, 4000, 3100, 3900, 3000 and 40000.
Is mean an appropriate average in this case. If no find the appropriate average. by Supriya Singla class ix Answered on Nov 1 at 7:45 p.m. I.S.T.
Answer 87. Mean salary = Some of all observations / No. of observatios
                                 = 71100 / 10
                                 = Rs.7110
Therefore mean is not appropriate average in this case.
The appropriate average is median
The observations in ascending oder are 3000, 3000, 3100, 3200, 3500, 3600, 3800, 3900, 4000, 40000
The middlemost terms are  n/2 =  10/2 =  5th  and  n/2  +  1  =  6th  (shown in pink)
Therefore  median salary = (3500 + 3600) / 2
                                  = Rs. 3550 which is clearly an appropriate average
Question 88.  Sir, May I know when will you provide CBSE social science sample papers for class X, by Pankaj garg, answered on Nov 03, 2007 at 9:40 p.m. I.S.T.
Answer 88. These papers will be available soon on cbsemath.com as well on our social science website cbsesocialscience.com
Question 89. prove that one of any three consecutive integer is divisible by 3? by archie prasad, answered on Nov 8, 2007 at 7:30 p.m. I.S.T.
Answer 89. Let the three consecutive numbers be n, n + 1, n + 2
By Euclid division algorithm
a = bq + r
For a = n, b = 3
n = 3q + r
r = 0, 1 or 2
Therefore n = 3q, 3q + 1, 3q + 2
when n = 3q
n = 3q is div by 3
but  n + 1 = 3q + 1
n + 2 = 3q + 2
are not divisible by 3
when n = 3q + 1
n = 3q + 1
n = 3q + 1 is not divisible by 3
n  + 1 = 3q + 2 is not divisible by 3
n  + 2 = 3q + 3 is divisible by 3
when n = 3q + 2
n = 3q + 2 is not div by 3
n + 1 = 3q + 3 is div by 3
n + 2 = 3q + 4 is not div by 3
Hence in all cases only 1 is div by 3
Question 90. 2 cubes of volume 64 cm^3 are joined end to end. Find the surface area of resulting cuboid, by Tripti shikha, Answered on nov 13 2007 at 11:06 P.M. I.S.T.
Answer 90. Side of each cube = cube root  of  64
                                     = 4 cm
Length of cuboid formed when the 2 cube are joined end to end = 4 + 4 = 8 cm.
breadth of cuboid = height of cuboid = 4 cm
now surface area of the cuboid = 2 (8×4+4×4+4×8)
                                          =  160 square cm

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