7 class SA1 answer key

SECTION-I

1.simplify 6× 9 – 6 ÷3 by BODMAS

Sol: 6× 9 – 6 ÷ 3
= 6× 9 – 2 ( division)
= 54 – 2 ( Multiplication)
= 52 (Subtraction)

2. Divide 39.54 by 6. Find the quotient.

Sol: 39.54 ÷ 6 = 6.59
The quotient is 6.59.

3. If ∠A+∠B = 90° then ∠A, ∠B are which type of angles.

Sol: ∠A+∠B = 90° then ∠A, ∠B are Complimentary angles.

4.Classify the following angles into acute and obtuse angles.

Sol: 20° and 47° are acute angles.
102° and 91° ate obtuse angles

SECTION-II

5.Solve the equation 10+6a=4 and check the result.

6a=4 –10
6a=–6
a=–`6/6`=–1

6.Which is grater than below.

i)2 × (–5) OR 3×(–4)
2 × (–5)=–10 and 3×(–4)=–12
So 2 × (–5) is greater than 3×(–4)
ii) (–6)×(–7) OR (–8)×5
(–6)×(–7)=42 and (–8)×5=–40
(–6)×(–7) is greater than (–8)×5

7.Write the equation of the following in mathematical statement

i) A number x decreased by 5 is 14
x – 5 =14
ii) Eight times of y plus 3 is –5
8y + 3 =–5

8. If x and x+40 are supplementary then find x

x°+x°+40°=180°
2x°=180°-40°
x=`140/2`=70°

9.Find the missing angles in each of the following triangle.

i)50°    ii)20°   iii)52°    iv)60°

SECTION-III

10 a) Calculate the following

i) 9.6 ÷ 16 =0.6
ii) 9.8 ÷ (-49)=-0.2
iii) –5.1 ÷ (–17)=0.3
iv) –3.8 ÷ 19=–0.2

b) Calculate the following

i) `16928/10`=1692.8
ii) `16928/100`=169.28
iii) `16928/1000`=16.928
iv)`16928/10000`=1.6928

11. a)Solve the following simple equations.

i) 3x=18
x=`18/3`=6

ii) -7m=21
m=`21/(-7)=-3`

iii)`(5m)/3`=10
5m= 10×3
m=`30/5`=6

iv) 4p+7=-21
4p= -21-7
p=`(-28)/4=-7`

b) The length of a rectangle is five more than twice of it's breadth.if the perimeter is 148 meters, then find the length and breadth of the rectangle.

Sol: Let Breadth = x
then Length = 2x+5
perimeter = 2( length+ breadth)
perimeter = 2(x+2x+5)
=2(3x+5)=6x+10
the perimeter is 148 meters. So
6x+10=148
6x= 148–10
x=`138/6`= 23
So the breadth is 23 meters and the length is 2×23+5=51 meters.

12 a) write the suitable number in blanks.

i) –3 + ---- = –3
–3 + 0 = –3

ii) 2 × (–3) = (–3) × ---
2 × (–3) = (–3) × 2

iii)–2 × --- = –2
–2 × 0 = –2

iv) -5 × --- = -30
–5 × 6 = –30

(OR)

b) Identify the laws in the following statements

i) –3 +5 = 5 +(–3)
Commutative property under addition

ii)–4 +0=0+(-4) =(–4)
Identity property under addition

iii)–2 × 1= 1×(–2)=–2
Identity property under Multiplication

iv) (–5×2)×3=(–5)×(2×3)
Associative property under Multiplication

13.a) observe the figure and fill the given table.

b) In the given figure AE is a straight line if the ratio of the angles ∠1,∠2,∠3,∠4 is 1:2:3:4 then find the angles

∠1+∠2+∠3+∠4 = 180°
sum of the ratio terms is 1+2+3+4=10
∠1=`180/10 × 1 =`18°
∠2=`180/10× 2 =` 36°
∠3= `180/10 ×3 =`54°
∠4=`180/10 ×4=`72°

BITS

14.`625/100=6.25`
15.0.11× 0.11 = 0.0121
16.100×0=0
17.5x-17=18 then value of x
5x=18+17=35
x=`35/5`=7
18.how many pieces each of length 1/2 m can be cut from a rope of length 60m is 120
19.If 2.5m and 1.5m as length and breadth of the rectangle then perimeter of the rectangle is
Sol:2(2.5+1.5)=2×4=8m
20.In a triangle two angles are 43°and 57°then third angle
Sol: 180°-43°-57°=80°
21.If x°+80°=180° then
Sol:x= 180° - 80° = 100°
22. -8 + 0 = -8
23.if `2/5` is proper fracton then `5/2` is Improper fraction
24.A Triangle can have One obtuse angle
25.5`1/3`= 5+`1/3`
26.If ∠A and ∠B are vertically opposite angles then ∠A=∠B
27.Loss of 500 represent by -500
28.8 times a number m is 24 represents 8m=24
29.Sum of three angles in a triangle ABC is straight angle
∠A+∠B+∠C=180°
30.Number of decimal places in the product 48.23 × 0.2 is three
31.which pair of angles form a linear pair 120° and 60°
32.Adjacent angles are observed in the following
example: Bullock cart wheel,Clock and Electric Pole
33.The acute angle between hands of clock at 2PM is 60°