২০৮১১
How many digits will be there to the right of the decimal point in the product of 95.75 and 0.2554?
উত্তর
6
সমাধান
As usual the number of digit to the right of a product of decimal system is the total number of digits to the right of the numbers. Here to the right of decimal point the number of digit is 7. But last two digit of the numbers are 5 and 4. Their product is (…5 x … 4 = … 20),20 which has a zero at the end. So, the number is 6.
২০৮১২
The sum of the ages of the son and father is 120 years. The father's age is 3 times than that of the son. What is the age of father?
উত্তর
90
সমাধান
let, age of son is x years
so the age of the father is 3x
according to the question,
x + 3x = 120
or, 4x = 120
∴ x = 30
so, father's age is = 3*30 = 90 years
২০৮১৪
The 2nd angle of a right triangle is 30 ডিগ্রী. Then what is the 3rd angle?
উত্তর
60ডিগ্রী
সমাধান
First,we know that all the angles in a triangle add up to 180 degrees.
Each triangle has 3 angles. Thus, we have the sum of three angles as shown:
180 = A + B + C
where we have angles A, B, and C. In our right triangle, one angle is 30 degree and we'll call that angle A. The other known angle is 90 degrees and we'll call this angle B. Thus, we have
180 = 30 + 90 + C
Simplify and solve for C.
180 = 120 + C
C = 60
২০৮১৫
The average of the two-digit numbers, which remain the same when the digits interchange their positions , is:
উত্তর
55
সমাধান
FALSE
২০৮১৬
Tanya's grandfather was 8 times older to her 16 years ago. He would bi 3 times of her age 8 years from now. Eight years ago, what was the ratio of Tanya's age to that of her grandfather?
উত্তর
None of these
সমাধান
Let, Tanya's age 16 years ago be x,
So grandfather's age 16 years ago = 8x.
8 years from now grandfather is three times of her age
= > 3(x + 16 + 8) = (8x + 16 + 8)
= > 3(x + 24) = (8x + 24)
= > 3x + 72 = 8x + 24
= > 5x = 48
= > x = 48/5
8 years ago ,the ratio was:
x + 8)/(8x + 8) = 48/5 + 8/8*48/5 + 5
= 48 + 40/384 + 40 = 88/424
= 11/53
Therefore,
the ratio of tanya's age to that of her grandfather = 11:53
২০৮১৭
x/2+3 = x/3+4. In this equation what is the value of x?
উত্তর
6
সমাধান
x/2 + 3 = x/3 + 4
or, x/2 - x/3 = 4 - 3
or, (3x - 2x)/6 = 1
∴ x = 6
ans: 6
২০৮১৮
What is the percentage to simple interest if the capital of 100 is doubled in 5 years?
উত্তর
20%
সমাধান
In 5 years, capital will be 200 tk
so, the interest = (200 - 100) = 100tk
we know, i = pnr
or, r = i/pn
or, r = 100/(100*5)
∴r = 1/5
the rae of simple interest = 1/5 * 100% = 20%
ans: 20%
২০৮১৯
The simple interest on a sum of money will be TK. 600 after 10 years. If the principal is trebled after 5 years , what will be the total interest at the end of the tenth year?
উত্তর
TK. 1200
সমাধান
In 10 years simple interest is 600 tk
In 5 years simple interest is ( 600×5)/10 = 300 tk
If principle is treabled interest will be treabled
In next 5 years in interest = (300×3) tk. = 900 tk
So, after 10 years total interest ( 900 + 300)tk = 1200 tk
২০৮২০
The average of 3 numbers is 7. If 2 of the numbers are zero, then what if the 3rd number?
উত্তর
21
সমাধান
given, average of 3 numbers is 7
and 2 of the numbers are zero
let the 3rd number is x
According to the question,
(x + 0 + 0)/3 = 7
or, x = 21
ans: 21