Maharashtra State Board 11th Maths Solutions Chapter 4 Determinants and Matrices Ex 4.5
From (i) and (ii), we get
A + B = B + A
Quesiton 8.
If A = ≤ft[{array}{cc}
1 & 2 i \\
-3 & 2
{array}] and B = ≤ft[{array}{cc}
2 i & 1 \\
2 & -3
{array} where i =, find A + B and A – B. Show that A + B is singular. Is A – B singular? Justify your answer.
Solution:
∴ By equality of matrices, we get
2a + b = 2 ….(i)
3a – b = 3 ….(ii)
c + 2d = 4 ….(iii)
2c – d = -1 ….(iv)
Adding (i) and (ii), we get
5a = 5
∴ a = 1
Substituting a = 1 in (i), we get
2(1) + b = 2
∴ b = 0
By (iii) + (iv) x 2, we get
5c = 2
∴ c =
Substituting c = in (iii), we get
+ 2d = 4
∴ 2d = 4 –
∴ 2d =
∴ d =
[Note: Answer given in the textbook is d = .
However, as per our calculation it is d = .]
ii. Both book shops got 10% profit in the month of August 2017.
For Suresh:
Profit for Physics books = = ₹ 665
Profit for Chemistry books = = ₹ 705.50
Profit for Mathematics books = = ₹ 890.50
For Ganesh:
Profit for Physics books = = ₹ 700
Profit for Chemistry books = = ₹ 750
Profit for Mathematics books = = ₹ 1020
[Note: Answers given in the textbook for Suresh’s profit in Chemistry and Mathematics books are ? 675 and ?850 respectively. However, as per our calculation profit amounts are ₹ 705.50 and ₹ 890.50 respectively.]