A picture of height 25mm is to be enlarged to a height of 1m by projecting it onto a screen which is 5m away from the projecting lens. Calculate, (I) the distance of the picture from the lens.
(II) the focal length of the lens

temp rises, and expansion

pretty sure it's false

r = ρ x length / area  

ρ = r x area / length  

ρ is in ohm-meters  

in basic units, it is m³kg/s³a²  

i think this is it.

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form