What’s the easiest way to find Lcm of lots of numbers that don’t go into each other?

I'm confused on this could anyone me and show me what i need to do to solve it.

15m is what percent of 60m; 3m; 30m; 1.5 km? the last one is km not m

Find the volume of the solid whose base is the region bounded by f(x), g(x) and the x-axis on the interval [0, 1], and whose cross-sections perpendicular to the y-axis are squares. your work must show the integral, but you may use your calculator to evaluate it. give 3 decimal places for your answe