posted by Mely .
The density of iron is 7.87 . What is the mass of a (variable l)* 4.00cm * 1.00 cm block of iron?
AND you can't have two unknowns. One is mass, the other is l. What is l?
However, you CAN solve for mass in terms of l.
v = length*4*1 = 4*length
mass = volume x density
mass = 4*length*7.87 = 31.48*length