Learn German: Das Bett ist schwer, es wiegt achtundvierzig Kilo. - The bed is heavy, it weighs forty-eight kilos.

In German, compound numbers between 21 and 99 are formed by putting the "ones" digit first, then und (and), and finally the "tens" digit. So, 48 is literally "eight-and-forty": acht + und + vierzig. Also, notice that these numbers are always mashed together into one single word!

Since the bed weighs 48 kilos, why isn't Kilo pluralized as "Kilos"?

In German, masculine and neuter units of measurement or weight (like Kilo, Gramm, or Liter) usually stay in their singular form when they come directly after a number. So you say ein Kilo (one kilo) and also achtundvierzig Kilo (forty-eight kilos).

Why do we use the pronoun es in the second part of the sentence?

The pronoun es (it) refers back to das Bett (the bed). Because Bett is a neuter noun—which we can tell from the "the" word das—you have to use the neuter pronoun es when you talk about it later in the sentence.

I learned that schwer means "difficult" or "hard". Why is it translated as "heavy" here?