Problem 1 :
The sides of the triangle are (x-1), x and (x+1). Find the sides of the triangle.
Solution :
Since the given are sides of the right triangle, the longest side is the hypotenuse.
(x+1)2 = (x-1)2 + x2
x2+2x+1 = x2-2x+1+x2
x2-4x = 0
x(x-4) = 0
x = 0 and x = 4
So, the sides of the triangle are 3, 4 and 5.
Problem 2 :
If A = {a, b, c, d, e, f, g, h} ,B = {a, b, e, f} and C = {a, c, e, g, h, k} find A - (B∪C).
Solution :
B∪C = {a, b, c, e, f, g, h, k}
A - (B∪C) = {a, b, c, d, e, f, g, h} - {a, b, c, e, f, g, h, k}
A - (B∪C) = {d}
Problem 3 :
What month is 19 months after July ?
Solution :
July corresponds to 7 in month arithmetic.
We want to know the day which is 19 months after July.
7 + 19 = 26
By dividing 26 by 12, we get 2 as remainder.
2 corresponds to February
So, the month which is after 19 months will be February.
Problem 4 :
A G.P consists of even number of terms. If sum of all the terms is three times of the odd number. Find the common ratio.
Solution :
Let the required geometric progression is having 4 terms.
a, ar, ar2, ar3
sn = a(1-rn)/(1-r)
Sum of above four terms :
s4 = a(1-r4)/(1-r)
Sum of odd terms :
a + ar2
= a(1+r2)
Sum of all terms = 3(sum of odd terms)
a(1-r4)/(1-r) = 3a(1+r2)
(1+r2)(1-r2)/(1-r) = 3(1+r2)
(1+r)(1-r)/(1-r) = 3
1+r = 3
r = 2
So, the common ratio is 2.
Problem 5 :
A rocket is in the form of a cylinder surmounted by a cone.The cylinder is of radius 2.5 m and the height 21 m and the cone has the slant height 6.5 m. Calculate the surface area of the rocket.
Solution :
Surface area of rocket = Curved surface area of cone + curved surface area of cylinder
= πrl + 2πrh
= πr(l+2h)
= (22/7) 2.5 (6.5+24)
= (22/7) 2.5 (30.5)
= 239.64
Problem 6 :
Find the value of a and b if ax3+bx2+7x+9 and x3+ax2-2x+b-4 when divided by x + 2 leave the remainders -13 and -16 respectively.
Solution :
Let p(x) = ax3+bx2+7x+9 and q(x) = x3+ax2-2x+b-4
x+2 = 0
x = -2
p(-2) = a(-2)3+b(-2)2+7(-2)+9
-13 = -8a+4b-14+9
-8a+4b = -13 + 5
-8a+4b = -8
Dividing by -4, we get
2a - b = 2 -----(1)
q(x) = x3+ax2-2x+b-4
q(-2) = (-2)3+a(-2)2-2(-2)+b-4
-16 = -8+4a+4+b-4
4a + b = -16+8
4a + b = -8 -----(2)
(1) + (2)
6a = -6
a = -1
By applying the value of a in (1), we get
-2-b = 2
-b = 4
b = -4
So, the values of a and b are -1 and -4.
Problem 7 :
Find the square root of 15625
Solution :
So, square root of 15625 is 125.
Problem 8 :
Determine the nature of the roots of the equation
x2-2x+5 = 0
Solution :
Nature of roots = b2 - 4ac
a = 1, b = -2 and c = 5
= (-2)2 - 4(1)(5)
= 4 - 20
= -16 < 0
It has no real roots.
Problem 9 :
Two poles of heights 6 m and 11 m stand on a plane ground. The distance between their feet is 12 m, find the distance between the tops.
Solution :
Distance between two poles = AE
In triangle ADE,
AE2 = AD2 + DE2
AE2 = 122 + 52
AE2 = 144+25
AE2 = 169
AE = 13
So, the distance between two poles.
Problem 10 :
Find the point which divides the line segment joining the points (2, 1) and (3, 5) externally in the ratio 2:3
Solution :
Required point = (lx2-mx1)/(l-m), (ly2-my1)/(l-m)
= [2(3)-3(2)]/(2-3), [2(5)-3(1)]/(2-3)
= (6-6)/5, (10-3)/(-1)
= (0, -7)
So the required point is (0, -7).
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