Average - Study Mode

[#186] A man spends his three months income in four month time. If his monthly income is Rs. 1,000 then his annual savings is.
Correct Answer

(A) Rs. 3,000

Explanation

Solution: According to the question, Annual income = 1,000 × 12 = Rs. 12,000 Annual expenditure = 1,000 × 9 = Rs. 9,000 Savings = Rs. 12,000 - Rs. 9,000 = Rs. 3,000

[#187] A factory buys 7 machines. 2 machine A, 2 Machine B and rest Machine C. Prices of the machines are Rs. 95000, Rs. 75000 and Rs. 43000 respectively. Calculate the average cost of these machines-
Correct Answer

(B) 67000

Explanation

Solution: $$eqalign{
& { ext{Given,}} cr
& herefore { ext{Total cost of the 7 machines}} cr
& = 95000 imes 2 + 75000 imes 2 + 43000 imes 3 cr
& = 190000 + 150000 + 129000 cr
& = { ext{Rs}}{ ext{. }}469000 cr
& x08ecause { ext{Average}} = frac{{{ ext{Total cost}}}}{{{ ext{Total number of machines}}}} cr
& = frac{{469000}}{7} cr
& = { ext{Rs}}{ ext{. }}67000 cr} $$

[#188] Average age of 7 students of a class is 28 years. Average age of first three students is 30 years. Age of fourth student is 4 years less than the age of fifth student. Ages of last two students is same and is 5 more than the average age of first three students. What is the average age of fourth and fifth student?
Correct Answer

(C) 18 years

Explanation

Solution: Total age of 7 students = 7 x 28 = 196 years Total age of first 3 students = 3 x 30 = 90 years 5 th student age = x years 4 th student age = (x + 4) years Age of 6 th and 7 th student = 30 + 5 = 35 years Total age of 7 students = 196 ⇒ 90 + (x + 4) + (x) + 35 + 35 = 196 ⇒ 2x = 196 - 164 ⇒ 2x = 32 ∴ x = 16 years Average of 4 th and 5 th student $$eqalign{
& = frac{{left( {x + 4}
ight) + x}}{2} cr
& = frac{{2 imes 16 + 4}}{2} cr
& = 18{ ext{ years}} cr} $$

[#189] Ras Bihari, a plumber, earned on an average Rs. 925 per day in the month of January. He earned on an average Rs. 881 per day during the first 20 days
and Rs. 915 per day during the last 20 days. What was his average income (in Rs.) per day from 12 th January to 20 th January?
Correct Answer

(D) 805

Explanation

Solution: Total earning in January = 925 × 31 = Rs. 28675 Earning of first 20 days = 881 × 20 = Rs. 17620 Earning of last 20 days = 915 × 20 = Rs. 18300 Earning of 12 th January to 20 th January = (17620 + 18300) - 28675 = 35920 - 28675 = Rs. 7245 ∴ Average of earning of 12 th January to 20 th January $$eqalign{
& = frac{{7245}}{9} cr
& = { ext{Rs}}{ ext{. 805}} cr} $$

[#190] 4 boys and 3 girls spent Rs. 120 on an average, of which boys spent Rs. 150 on the average. The the average amount spent by the girls is-
Correct Answer

(A) Rs. 80

Explanation

Solution: According to the question, Average : 4B + 3G = Rs. 120 Sum : 4B + 3G = 120 × 7 = Rs. 840 Average : 4B = 150 × 4 = Rs. 600 Sum of girls = 840 - 600 = Rs. 240 Average of girls = $$frac{240}{3}$$ = Rs. 80