2.1. A metal weight has a mass of 20 kg and is an alloy of four metals. The first metal in this alloy is one and a half times more than the second, the mass of the second metal is to the mass of the third as $3: 4$, and the mass of the third to the mass of the fourth - as $5: 6$. Determine the mass of the fourth metal. Give the answer in kilograms, rounding to hundredths if necessary.

$\{5.89\}$
Solution. The masses are in the ratio 45:30:40:48. The total sum $=163 x$. Therefore, $x=20 / 163$. The mass of the fourth metal is 48 times greater.