Linear equations and inequalities

1003197407

Level: 
C
A hose can fill the garden pool in \( 20 \) hours. The owners bought a pump that guarantees filling the pool in \( 8 \) hours. However, a crack appeared in the pool's shell which can drain all the water from the full pool within \( 5 \) days. How long will it take to fill the pool with the hose and the pump at the same time as the water runs off through the crack?
exactly \( 6 \) hours
approximately \( 5.7 \) hours
approximately \( 5.5 \) hours
approximately \( 6.8 \) hours

1003197408

Level: 
C
The painter \( A \) takes \( 15 \) hours to paint a flat. The painter \( B \) takes \( 12 \) hours to paint the same flat and the painter \( C \) takes \( 10 \) hours to complete the same task. The painter \( A \) starts to paint alone and after \( 2 \) hours joins him the painter \( B \). After the next hour the painter \( C \) starts to paint with them too. How long will all three painters paint together before completing the work?
\( 2\,\mathrm{h}\ 52\,\mathrm{min} \)
\( 3\,\mathrm{h}\ 8\,\mathrm{min} \)
\( 3\,\mathrm{h}\ 24\,\mathrm{min} \)
\( 4\,\mathrm{h} \)

9000018010

Level: 
C
The salary of Peter has been increased by \(\$2\: 400\). The salary of Jane increased by \(3\, \%\) and this increase has been bigger than the increase of the Peter's salary. In the following list identify a possible old salary of Jane.
\(\$81\: 000\)
\(\$80\: 000\)
\(\$9\: 000\)
\(\$8\: 000\)

9000018110

Level: 
C
Consider a coil composed from a ferrite core and a wire winding. The mass of the core is \(2\, \mathrm{kg}\). The material for the wire is such that the mass of the wire of the length \(30\, \mathrm{m}\) is bigger than the mass of the wire of the length \(10\, \mathrm{m}\) together with the ferrite core. In the following list identify a possible mass of one meter of the wire.
\(110\, \mathrm{g}\)
\(100\, \mathrm{g}\)
\(0.01\, \mathrm{kg}\)
\(0.09\, \mathrm{kg}\)