Question 696964
You have 2 equations, 1 for before road repairs
and another after road repairs start
Let {{{ d }}} = distance in km covered before and after road repairs start
Let {{{ s }}} = the current speed limit in km/hr
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Driving at the speed limit before and after the repairs:
Before:
(1) {{{ d = s*2 }}}
After:
(2) {{{ d = ( s - 40 )*3.6 }}}
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substitute (1) into (2)
{{{ 2s = ( s - 40 )*3.6 }}}
{{{ 2s = 3.6s - 144 }}}
{{{ 1.6s = 144 }}}
{{{ s = 90 }}}
The speed limit now is 90 km/hr
check the answer:
(1) {{{ d = s*2 }}}
(1) {{{ d = 90*2 }}}
(1) {{{ d = 180 }}}
and
(2) {{{ d = ( s - 40 )*3.6 }}}
(2) {{{ d = ( 90 - 40 )*3.6 }}}
(2) {{{ d = 50*3.6 }}}
(2) {{{ d = 180 }}}
OK