Thallium has two isotopes thallium-203 and thallium-205 find which isotope is more abundant\abundance

Let we have X of Tl-205 so the percent of Tl-203 will be 100-X

Average mass of  Thallium is 204.4

Mass of  Tl-205=  

Mass of  Tl-203=  

So,

205X +20300-203X=20440

X=70

So the percent or abundance of  Tl-205 is 70 while that of Tl-203 will be 30.

a: 45.9 meters

b: 4.29 seconds

step-by-step explanation:

a: h(t)=1/2(-9.8)(3)^2+0(3)+90

h(t)=-4.9(3)^2+90

h(t)=-44.1+90

h(t)=45.9 meters

b: 0=1/2(-9.8)(t^2)+0t+90

0=-4.9t^2+90

-90=-4.9t^2

18.37=t^2

t=4.29 seconds

in the second question, the numbers aren't exact, but they're a close approximation.