২২৩৯১
One day at a school, one -twelfth of the students were absent and 20% of those present went on a field trip. If the number of students staying back in the school that day was 660, how many students are enrolled at that school?
উত্তর
900
সমাধান
Student staying at the school is (100 - 20 = 80%) of the present students.
80% of the present students = 660
So, 100% or total present students = 660 x 100 / 80 = 825
But, present students = (1 - 1/12 = 11/12) of all enrolled students
Now, 11/12 of enrolled students = 825
So, all enrolled students = 825 x 12 / 11 = 900
২২৩৯২
If a person can save TK.380 in 5 weeks, in how many weeks, at this same rate, can the person save 2.6 times amount?
উত্তর
13
সমাধান
Total savings will be TK. 380x2.6 or TK. 988
So in one week he can save TK. 380/5 or TK. 76
Number of weeks need for saving TK. 988 is 988/76 or 13
২২৩৯৩
Mr. Karim purchased TK. 600 worth of traveler's cheques. If each cheque was worth either TK. 20 or TK. 50, which of the following cannot be the number of TK. 20 cheques purchased?
উত্তর
18
সমাধান
10*20 = 200...rest 400 is divisible by 50
15*20 = 300...rest 300 is divisible by 50
20*20 = 400...rest 200 is divisible by 50
but 18*20 = 360...rest 240 is not divisible by 50
ans 18
২২৩৯৫
The area of a rectangle is 200 sq. meter. If the length is twice the breadth , what is the perimeter of the rectangle?
উত্তর
60
সমাধান
Let L be the length and B be the breadth.
So, L x B = 200
or, 2B x B = 200
or, B2 = 100
or, B = 10
So, L = 2B = 2 x 10 = 20
Therefore, the perimeter of the rectangle = 2 (L + B) = 2 (20 + 10) = 2 x 30 = 60.
২২৩৯৬
Perimeter of rectangle is 200 meter. Its width is 3/7 of its length. What is the length in meter?
উত্তর
70
সমাধান
In case of a rectangle,
2(Length + Width) = perimeter
or, 2(Length + 3/7 of Length) = 200
or, 10/7 of Length = 200/2
So, Length = 200/2 x 7/10 = 70 meter
২২৩৯৭
A company makes a profit of 5% in its first TK. 1000 of sales each day , and 4% on all sales in excess of TK. 1000 for that day. What would be the profit of the company in day when sales are TK. 6000?
উত্তর
250
সমাধান
Profit for first 1000 TK sales = 5% of 1000 = 5/100 of 1000 = 50 TK
Profit for Excess (6000 - 1000 = 5000) TK sales = 4% of 5000 = 4/100 of 5000 = 200 TK
Total profit = 50 + 200 = 250 TK
২২৩৯৮
How much interest will TK. 2000 earn at an annual rate of 10% in one year if the interest is compounded every 6 months?
উত্তর
None of these
সমাধান
C = P(1 + r/n)nt [C = principal with interest, P = principal, r = rate of interest, n = number of times interest is compounded per time period, t = number of time periods]
Here, P = 2000, r = 10% = 10/100 = 0.1, n = 2, t = 1
So, interest, I = C - P = 2000(1 + 0.1/2)2x1 - 2000 = 2000x1.052 - 2000 = 205 TK
২২৩৯৯
The monthly salary of a person is increased by 10% in one month, but is decreased by 10% in the next month. What is the age of their father?
উত্তর
None of these
সমাধান
the quesion is wrong. it should be -
The monthly salary of a person is increased by 10% in one month, but is decreased by 10% in the next month. What's the percentage change in his salary?
Solution:
Let the initial salary be 100 tk.
Increase by 10% will imply = 100 + 100x10/100 = (100 + 10) = 110 tk.
Decrease by 10% will mean = 90% of 110 = 99
Hence the effective change is a decrease by = (100 - 99)% = 1%. (ans)
২২৪০০
Average age of three brothers is 16 years. Average age of these brothers along with their father is 25 years. What is the age of their father?
উত্তর
52
সমাধান
Total age of the three brothers = 3 x 16 = 48 years
Total age of the brothers along with their father = 4 x 25 = 100
So, age of the father = 100 - 48 = 52 years