Question 344406
Let {{{a}}} = kg of 11 rs/kg rice needed
Let {{{b}}} = kg of 2 rs/kg rice needed
{{{11a}}} = cost of 11 rs/kg rice
{{{2b}}} = cost of 2 rs/kg rice
{{{7*171}}} = cost of 7 rs/kg rice
given:
(1) {{{a + b = 171}}}
{{{11a + 2b = 7*171}}}
(2) {{{11a + 2b = 1197}}}
Multiply both sides of (1) by {{{2}}}
and subtract (1) from (2)
(2) {{{11a + 2b = 1197}}}
(1) {{{-2a - 2b = -342}}}
{{{9a = 855}}}
{{{a = 95}}}
The quantity of 11 rs/kg rice needed is 95 kg
And, from (1):
{{{a + b = 171}}}
{{{95 + b = 171}}}
{{{b = 76}}}
check answer:
(2) {{{11a + 2b = 1197}}}
(2) {{{11*95 + 2*76 = 1197}}}
{{{1045 + 152 = 1197}}}
{{{1197 = 1197}}}
OK