Two diggers

There are two diggers. One digger digs a pit 46 hours second gidding 2 times faster.

a) how long took to dig a pit second digger
b) how long took dig together


Correct result:

a =  23 h
b =  15.33 h

Solution:

$a=46\mathrm{/}2=23\text{ h}$

$$\begin{gathered} b({\displaystyle \frac{1}{46}}+{\displaystyle \frac{1}{a}})=1 \\ b={\displaystyle \frac{1}{{\displaystyle \frac{1}{46}}+{\displaystyle \frac{2}{46}}}}=15.33\text{ h} \end{gathered}$$

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