Question 666802
isa wants to cover a 6-mile course in 1 hour by running part of the course and walking the rest.
 she also want to take a 5 minute water break.
 lisa runs at 8mi/h and walks at 3 mi/h.
 How many miles will she have to run?
:
Let r = no. of miles to be run
then
(6-r) = no. of miles to be walked
:
Write a time equation; time = dist/speed
Change a 5 min break to 5/60 = 1/12 hr
:
run time + break + walk time = 1 hr
{{{r/8}}} + {{{1/12}}} + {{{((6-r))/3}}} = 1
:
multiply by 24 to clear the denominators, results:
3r + 2 + 8(6-r) = 24
:
3r + 2 + 48 - 8r = 24
3r - 8r + 50 = 24
-5r = 24 - 50
-5r = -26
r = {{{(-26)/(-5)}}}
r = +5.2 mi running
:
:
Check this, walking distance: 6 - 5.2 = .8 min
{{{5.2/8}}} + {{{1/12}}} + {{{.8/3}}} =
use a calc, it totals 1 hr