যদি 8Pr = 336 হয়, তাহলে r এর মান কত?
A
3
B
4
C
7
D
5
উত্তরের বিবরণ
প্রশ্ন: যদি 8Pr = 336 হয়, তাহলে r এর মান কত?
সমাধান:
8Pr = 336
⇒ 8!/(8 - r)! = 336 [আমরা জানি, nPr = n!/(n - r)!]
⇒ 40320/(8 - r)! = 336
⇒ (8 - r)! = 40320/336
⇒ (8 - r)! = 120
⇒ (8 - r)! = 5! [5! = 5 × 4 × 3 × 2 × 1 = 120]
⇒ 8 - r = 5
⇒ r = 8 - 5
∴ r = 3
0
Updated: 1 month ago
a + b + c = 0 হলে a3 + b3 + c3 এর মান কত?
Created: 5 months ago
A
abc
B
3abc
C
6abc
D
9abc
প্রশ্ন: a + b + c = 0 হলে a3 + b3 + c3 এর মান কত?
সমাধান:
a + b + c = 0
a + b = - c
এখন
a3 + b3 + c3
= (a + b)3 - 3ab(a + b) + c3
= (- c)3 - 3ab(- c) + c3
= - c3 + 3abc + c3
= 3abc
0
Updated: 5 months ago
f(x) = x3 - mx2 + 7x - 10 হয়, তাহলে m এর কোন মানের জন্য f(2) = 0 হবে?
Created: 2 months ago
A
- 1
B
4
C
- 2
D
3
প্রশ্ন: f(x) = x3 - mx2 + 7x - 10 হয়, তাহলে m এর কোন মানের জন্য f(2) = 0 হবে?
সমাধান:
দেওয়া আছে,
f(x) = x3 - mx2 + 7x - 10
= (2)3 - m(2)2 + 7(2) - 10
= 8 - 4m + 14 - 10
= 12 - 4m
এখন,
f(2) = 0
⇒ 12 - 4m = 0
⇒ 4m = 12
∴ m = 3
0
Updated: 2 months ago
Two pipes A and B can fill the tank in 24 and 36 minutes, respectively. Both the pipes are opened together. After how many minutes should the pipe B be turned off, so that the tank be fill in 18 minutes?
Created: 1 month ago
A
9 minutes
B
12 minutes
C
10 minutes
D
16 minutes
Question: Two pipes A and B can fill the tank in 24 and 36 minutes, respectively. Both the pipes are opened together. After how many minutes should the pipe B be turned off, so that the tank be fill in 18 minutes?
Solution:
Given that,
Pipe A fills the tank in 24 minutes.
Pipe B fills the tank in 36 minutes.
Total time to fill the tank = 18 minutes.
Now,
LCM of 24 and 36 = 72 (Total capacity of the tank).
Efficiency of pipe A = 72/24 = 3 units/minute.
Efficiency of pipe B = 72/36 = 2 units/minute.
Let,
pipe B be turned off after x minutes.
Pipe A works for 18 minutes.
Pipe B works for x minutes.
Work done by A in 18 minutes = 3 × 18 = 54 units.
Work done by B in x minutes = 2x = 2x units.
Total work done = 54 + 2x = 72
⇒ 2x = 72 - 54
⇒ 2x = 18
⇒ x = 18/2
∴ x = 9
∴ Pipe B should be turned off after 9 minutes.
0
Updated: 1 month ago
