Tanya and her brother are racing with their new bikes in the neighborhood. Their block is one mile long. Tanya's average speed is 0.15 mi/s and her brother's is 0.11 mi/s. Who will reach the end of block first, and how much time ahead of the other will they be?

Ahypothetical metal has an orthorhombic unit cell for which the a, b, and c lattice parameters are 0.413 nm, 0.665 nm, and 0.876 nm, respectively. (a) if there are 8 atoms per unit cell and the atomic packing factor is 0.536, determine the atomic radius (in nm). (b) if the density is 3.99 g/cm3, calculate the metal's atomic weight (in g/mol).