# A Typist Charges Rs. 145 for Typing 10 English and 3 Hindi Pages, While Charges for Typing 3 English and 10 Hindi Pages Are Rs. 180. Using Matrices, Find the Charges of Typing One English and One Hindi Page Separately. - Mathematics

A typist charges Rs. 145 for typing 10 English and 3 Hindi pages, while charges for typing 3 English and 10 Hindi pages are Rs. 180. Using matrices, find the charges of typing one English and one Hindi page separately. However typist charged only Rs. 2 per page from a poor student Shyam for 5 Hindi pages. How much less was charged from this poor boy? Which values are reflected in this problem?

#### Solution

Let charges for typing one English page be Rs. x.

Let charges for typing one Hindi page be Rs.y.

Thus from the given statements, we have,

10x+3y=145

3x+10y=180

Thus the above system can be written as,

[(10,3),(3,10)][(x),(y)]=[(145),(180)]

⇒ AX = B, where, A=[(10,3),(3,10)],x=[(x),(y)] " and " B = [(145),(180)]

Multiply A-1 on both the sides, we have,

A-1 x AX = A-1B

⇒ IX = A-1B

⇒ X = A-1B

Thus, we need to find the inverse of the matrix A.

We know that, if P=[(a,b),(c,d)] " then " P^(-1) = 1/(ad-bc)[(d,-b),(-c,a)]

Thus, A^(-1)=1/(10xx10-3xx3)[(10,-3),(-3,10)]

= 1/(100-9)[(10,-3),(-3,10)]

=1/91[(10,-3),(-3,10)]

Therefore, X=1/91[(10,-3),(-3,10)][(145),(180)]

=1/91[(10xx145-3xx180),(-3xx145+10xx180)]

=1/91[(910),(1365)]

=[(10),(15)]

=>[(x),(y)][(10),(15)]

⇒ x = 10 and y=15

Amount taken from Shyam = 2 × 5 = Rs.10

Actual rate = 15 × 5 =75

Difference amount = Rs.75 – Rs.10 = Rs.65

Rs. 65 less was charged from the poor boy Shyam.

Humanity and sympathy are reflected in this problem.

Concept: Inverse of Matrix - Inverse of a Nonsingular Matrix by Elementary Transformation
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