Maria Petrovna is walking down the road at a speed of 4 km/h. Seeing a stump, she sits on it and rests for the same whole number of minutes. Mikhail Potapovich is walking down the same road at a speed of 5 km/h, but sits on each stump twice as long as Maria Petrovna. They both set out and arrived at the same time. The length of the road is 11 km. How many stumps could there be on the road?
Mary Petrovna overcomes the specified distance in ${ }^{11} / 4$ hours, while Mikhail Potapovich does it in $11 / 5$ hours.

Therefore, Mary Petrovna rests for

$11 / 4-11 / 5=11 / 20$ hours (which is 33 minutes) longer.

Since Mary Petrovna sits on each stump for a whole number of minutes and the number of stumps is also a whole number, she could have sat on each stump for $33, 11, 3$ or 1 minute, which corresponds to 1, 3, 11 or 33 stumps.

## Answer

$1, 3, 11$ or 33 stumps.