Question 413255
1st 2 km:
(1) {{{2 = r[1]*t[1]}}}
2nd 2 km:
(2) {{{2 = .5*r[1]*t[2]}}}
(3) {{{t[1] + t[2] = .5}}} hr
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(3) {{{t[2] = .5 - t[1]}}}
and
(1) {{{t[1] = 2/r[1]}}}
and
(2) {{{2 = .5*r[1]*(.5 - t[1])}}}
(2) {{{2 = .5*r[1]*(.5 - 2/r[1])}}}
(2) {{{2 = .25*r[1] - 1)}}}
(2) {{{.25r[1] = 3}}}
(2) {{{r[1] = 12}}}
and
{{{r[2] = .5r[1]}}}
{{{r[2] = 6}}} km/hr
Coach ran the 3rd km at 6 km/hr
check answer:
(1) {{{t[1] = 2/r[1]}}}
(1) {{{t[1] = 2/12}}}
(1) {{{t[1] = 1/6}}}
(3) {{{t[1] + t[2] = .5}}}
(3) {{{t[2] = 3/6 - 1/6}}}
(3) {{{t[2] = 1/3}}}
{{{t[1] + t[2] = 1/6 + 2/6}}}
{{{t[1] + t[2] = .5}}} hr
OK