help! please give me the answers ...no need of explaination ...please help me !! guys ..m in grade 9 cbse ..this is my model paper
Answers
Answer:
Step-by-step explanation:
Section - A
1) a
To find the co-ordinates, x-axis represents the plain mirror. M is the point in the rectangular axes in the fourth quadrant whose co-ordinates are (4, -3).
When this point reflected in x-axis, the image is formed in the first quadrant whose co-ordinates are (4, 3).
2) None of the answers are correct.
By identity
a3 + b3 + c3 – 3abc = (a+b+c)(a2+b2+c2 – ab - bc - ca)
which implies
a3 + b3 + c3 = 3abc if a + b + c = 0
Here a + b + c= 30 + 20 – 50 = 0
which means
30³+20³+(-50)³ = 3 * 30 * 20 * (-50) = - 90000
3) a
One of angles = 65 degrees.
Let one angle be x, so the other angle is x + 25 (because is diff. is 25 degrees)
Sum of all angles in triangle = 180
65 + x + x + 25 = 180.
2x = 90 => x = 45 degrees.
Other angle = 45 + 25 = 70 degrees.
4) d
In a Square, two diagonals are equal.
But since this is not one of the options, the closest that can come is trapezium. Diagonals are equal only in the special case of trapezium called trapezoid (or isosceles trapezium).
5) b
X31 + 30 = (-1)31 + 30 = -1 + 30 = 29.
Section - B
6. 0
a + b = 2
cubing on both sides
(a+b)3 = (2)3
=> a3 + b3+ 3ab(a+b) = 8
=> a3 + b3+ 3ab(2) = 8
=> a3 + b3+ 6ab – 8 = 0
7. 16✓3 cm²
Heron's formula for calculation of Area of an triangle → ✓s(s-a)(s-b)(s-c)
Where, s= Semi-perimeter and a,b and c are sides of Triangle respectively.
So here, all sides are equal and each side = Perimeter/3 (As Triangle it Equilateral and formula for perimeter for triangle is 3×side and for side it'll be Perimeter/3)
= 24/3 = 8cm
Semi perimeter = 24/2 = 12cm
Now apply the Heron's formula →
✓12(12-8) (12-8) (12-8)
= ✓12×4×4×4
= ✓2×2×2×2×2×2×2×2×3
= 2×2×2×2×✓3
= 16✓3 cm²
The area of Equilateral Triangle with side 8 cm is 16✓3 cm².
8. a=4 and b=4
A (4,6)
x=4 ,y=6
a(4)+b(6)=8
4a+6b=8 ======(1)
Then, B(1,3)
x=1 ; y=3
a+3b=8 =========(2)
Multiply equation 2 by 4 and solve both equations
Solving 1 and 2 we get,
b=4 and a=4
Now for question 9 and section C, please look at the attachment.
