Expression : (3 \(\times\) 8) - 5
Tree Diagram

(i) Given
1^st month = 1210
2^nd month = 2100
3^rd month = 2550
4^th month = 3160
5^th month = 3310
Tree diagram

Total = 1210 + 2100 + 2550 + 3160 + 3310.
ii) Given
Ram had a bank deposit = Rs. 7,55,250
He had withdrawn = Rs. 5,34,500
Therefore the amount left in his amount
= Rs. 7,55,250 - Rs. 5,34,500
Tree diagram

iii) Given
No. of bicycles produced in 1 day = 1,600
No. of bicycles produced in 20 days
= 1600 \(\times\) 20
Tree Diagram

iv) Given
Total amount = Rs. 90,000
No. of employees = 30
= 90,000 / 30
Tree Diagram

(i) 80°, 60° 
The sum of 3 angles of triangle = 180° 
Let A = 80° , B = 60° , C = ?
A + B + C = 180° 
80° + 60° + C = 180° 
= 180° - (80° + 60°)
C = 180° - 140° = 40° 
Therefore third angle = 40° 
(ii) 75°, 35°
The sum of 3 angles of triangle = 180° 
Let A = 75°, B = 35°, C = ?
A + B + C = 180° 
75° + 35° + C = 180° 
= 180° - (75° + 35°)
C = 180° - 110° = 70° 
Therefore third angle = 70° 
(iii) 52°, 68°
The sum of 3 angles of triangle = 180° 
Let A = 52°, B = 68°, C = ?
A + B + C = 180° 
52 + 68 + C = 180° 
= 180° - (52° + 68°)
C = 180° - 120° = 60° 
Therefore third angle = 60° 
(iv) 50°, 90°
The sum of 3 angles of triangle = 180° 
Let A = 50°, B = 90°, C = ?
A + B + C = 180° 
50° + 90° + C = 180° 
= 180°  - (50° + 90°)
C = 180° - 140° = 40°
Therefore third angle = 40°
(v) 120°, 30° 
The sum of 3 angles of triangle = 180°
Let A = 120°, B = 30°, C = ?
A + B + C = 180°
75° + 35° + C = 180°
= 180° - (120°+ 30°)
C = 180° - 150 = 30°
Therefore third angle = 30°
(vi) 55°, 85°
The sum of 3 angles of triangle = 180°
Let  A = 55°, B = 85°, C = ?
A + B + C = 180°
55° + 85° + C = 180°
= 180° - (55° + 85°)
C = 180° - 140°= 40°
Therefore third angle = 40°

(i) 8 cm, 6 cm, 4 cm
The sum of two smaller sides
= 6 cm + 4 cm = 10 cm > 8 cm, the third side.
It is greater than the third side
So, yes a triangle can be formed.
Type: Scalene triangle.
(ii) 10 cm, 8 cm, 5 cm.
The sum of two smaller sides
= 8 cm + 5 cm = 13 cm > 10 cm, the third side.
It is greater than the third side.
Therefore, yes a triangle can be formed.
Type: Scalene triangle. 
(iii) 6.2 cm, 1.3 cm, 3.5 cm.
The sum oftwo smaller sides
= (1.3 + 3.5) cm = 4.8 cm < 6.2 cm It is
lesser than the third side.
Therefore, no a triangle cannot be formed.
(iv) 6 cm, 6 cm, 4 cm.
The sum of two smaller sides
= 6 cm + 4 crn = 10 cm > 6 cm, the third side.
It is greater than the third side.
Therefore, yes a triangle can be formed
Type: Isoceles triangle.
(v) 3.5 cm, 3.5 cm, 3.5 cm
The sum of two smaller sides = (3.5 + 3.5) cm = 7 cm > 3.5 cm
Therefore, it s greater than the third side.
Yes a triangle can be formed.
Type: Equilateral triangle
(vi) 9 cm, 4 cm, 5 cm
The sum of two smaller sides = 4 cm + 5 cm = 9 cm = 9 cm
Therefore, it s equal to the third side.
No, a triangle cannot be formed.

Selling price = Rs. 1550
Profit = Rs. 150
Profit = S.P. - C.P.
\(\Rightarrow\) Rs. 150 = Rs. 1550 - C.P.
\(\Rightarrow\) Cost price = Rs.1550 - Rs. 150 = Rs. 1400

Time slowed down for 1 hour = 2 minutes
Time slowed down for 11 hours =11 \(\times\) 2 = 22 minutes
So, at 6 p.m the clock slows down by 22 minutes. That means the clock shows 5 hours 38 minutes at 6 p.m.

This is a LCM related sum. So, we need to find the LCM of 15, 20, 25 and 30.

The LCM of 15, 20, 25 and 30 is 2 \(\times\) 2 \(\times\) 3 \(\times\) 5 \(\times\) 5
= 300 minutes = 5 \(\times\) 60 minutes = 5 \(\times\) 1 hour = 5 hours
Thus, the four Mobile Phones will ring together again at 10.00 a.m.

Let us find the factors of 18, 24 and 30 (use of divisibility test rules will also help).
The factors of 18 are  9 and 18.
The factors of 24  8, 12 and 24.
The factors of 30 are  10, 15 and 30.
The factors that are common to all the three given numbers are 1, 2, 3 and 6 of which 6 is the highest.
Hence, HCF (18, 24, 30) = 6.
Note that 1 is a trivial factor of all numbers.
Let us find the factors of 24 by tree method.

Here, 24 = 2 \(\times\) 2 \(\times\) 2 \(\times\) 3
Similarly, we can find the factors of 18 and 30.