২২৪৯১
1 + 2 + 3 +.................. + 100 =?
উত্তর
5050
সমাধান
এখানে, মোট পদ n = 100
∴ সমষ্টি S = n(n + 1)/2
= 100(100 + 1)/2
= (100×101)/2
= 5050
২২৪৯২
Murad bought equal number of 20-paisa stamps and 30-paisa stamps the Murad bought?
উত্তর
40
সমাধান
the Question is wrong.it should be -
"Murad bought equal numbers of 20 - paisa and 30 - paisa stamps. If the total cost of the stamps was Tk.10.00, what was the total number of stamps bought? "
Slution:
ATQ,
20x + 30x = 10 × 100
= > 50x = 1000
= > x = 1000/50
∴x = 20
অর্থাৎ সে মোট দুই প্রকারের Stamp কিনেছিল = 20 + 20 = 40 টি । (ans)
২২৪৯৩
Half of the student of a school play football and one third of the rest play cricket. The remaining 300 students do not play either of the games. How many students are there in the school?
উত্তর
900
সমাধান
Fraction of students playing Football = 1/2
Fraction of students playing Cricket = 1/3 of the remaining 1/2 = 1/6
Now, fraction of the students not playing either of the games = 1 - (1/2 + 1/6) = 1 - (3 + 1)/6 = 1/3
According to the question, 1/3 of the students = 300
So, the number of total students = 300 x 3 = 900.
২২৪৯৪
Karim has exactly 3 times as many Bangladesh as non-Bangladesh stamps in his collection. Which of the following cannot be the number of stamps in Karim's collection?
উত্তর
54
সমাধান
Here, the ratio is 3 : 1. The total number of stamps must be divisible by the sum of the ratios which is (3 + 1 = 4). Only the number 54 is not divisible by 4. So, 54 cannot be the total number of stamps in his collection.
২২৪৯৫
Salam's average in four test is 80%. What mark does she need to score in her fifth test to make her average 84%?
উত্তর
100%
সমাধান
the sum of the first 4 test scores is 4*80 = 320.
the sum of ALL 5 scores to be 5*84 = 420.
∴she need score in her fifth test = 420 - 320 = 100. (ans)
২২৪৯৬
From 2004 to 2005. the sales of a book decreased by 80%. If the sales in 2006 were the same as in 2004, by what percent did they increase from 2005 to 2006?
উত্তর
400%
সমাধান
let, 100 copies were sold in 2004
∴copies sold in 2005 = 100 - 80 = 20
copies sold in 2006 = 100
so, required increase = (100 - 20)/20 × 100 = 400% (ans)
২২৪৯৭
Three-fourth petrol of a reservoir is used to fill the petrol tanks of five trucks having the same storage capacity. What part of the total capacity of the petrol reservoir did each truck receive?
উত্তর
3/20
সমাধান
Let the capacity of each truck and the reservoir be T and R respectively.
Total capacity of five trucks = 5T
According to the question, 5T = 3/4 of R
or, T = 3/4 x R / 5 = (3/20) R
So, each truck received 3/20 of the reservoir.
২২৪৯৮
The average of 10 numbers is ---10. If the sum of 6 of them is 100, then what is the average of the other 4 numbers?
উত্তর
-50
সমাধান
Total of 10 numbers = - 10×10 = - 100
the sum of 6 numbers is 100
so,Sum of last 4 numbers = - 100 - 100 = - 200
∴Average = - 200/4 = - 50 (ans)
২২৪৯৯
If x% of y is 10, then what is y?
উত্তর
1000/x
সমাধান
ATQ,
x% of y = 10
or, xy/100 = 10
or, xy = 1000
or, y = 1000/x
ans: 1000/x
২২৫০০
Three times a number minus 7 is 32. What is the twice of the number?
উত্তর
26
সমাধান
Let the number be N.
According to the question,
3N - 7 = 32
or, 3N = 32 + 7 = 39
So, N = 39/3 = 13
Therefore, twice of N or 2N = 2 x 13 = 26.