# Math Help - Help thease problems problems

1. ## Help thease problems problems

1) m : n = 1 : 4, n : p = 4 : 5. If p =1000, find m.

2) The circumference of a circle is 1, find the central angle corresponding to the arc which 2/5 long

2. Originally Posted by sri340
1) m : n = 1 : 4, n : p = 4 : 5. If p =1000, find m.
n: p = 4:5

so
5n = 4p = 4(1000) = 4000

thus
n = 800

Again
m:n = 1:4

so
4m = n = 800

thus
m = 200

-Dan

3. Originally Posted by sri340
1) m : n = 1 : 4, n : p = 4 : 5. If p =1000, find m.
you have $\frac mn = \frac 14 \implies n = \frac 1{4m}$

you also have $\frac np = \frac 45 \implies n = \frac 4{5p}$

but we found that $n = \frac 1{4m}$

thus, $\frac 1{4m} = \frac 4{5p}$

$\Rightarrow m = \frac {5p}{16}$

now continue

2) The circumference of a circle is 1, find the central angle corresponding to the arc which 2/5 long
do you work in radians or degrees?