4. During May, June, July, and August (a total of 123 days), Andrija waters the flowers and mows the lawn for his neighbors. The lawn needs to be mowed every sixth day, and the flowers need to be watered every third day. He earns 2 euros and 40 cents for each mowing and 75 cents for each watering. One-third of his total earnings over these four months, Andrija plans to donate to humanitarian causes. How much money will he donate if he mowed the lawn and watered the flowers on May 1st?
First solution.

Since $123 \div 6 = 20$ with a remainder of 3, and $123 \div 3 = 41$, we conclude that Andrija mowed the lawn for his neighbors 20 times and watered the flowers 41 times.

$1 \text{ POINT}$

For each mowing, he earns 2 euros and 40 cents, so for 20 mowings, he earned:

$20 \cdot 2$ euros $= 40$ euros

$20 \cdot 40$ cents $= 800$ cents

$1 \text{ POINT}$

40 euros and 800 cents $= 48$ euros

$1 \text{ POINT}$

For each watering, he earns 75 cents, so for 41 waterings, he earned:

$41 \cdot 75$ cents $= 3075$ cents $= 30$ euros and 75 cents.

$1 \text{ POINT}$

In total, he earned 78 euros and 75 cents.

$1 \text{ POINT}$

Since he plans to donate one-third of his earnings, and $78 \div 3 = 26$ and $75 \div 3 = 25$, he will donate 26 euros and 25 cents.

$1 \text{ POINT}$

TOTAL 6 POINTS

Note: Students can convert all amounts to cents and calculate that for one mowing, Andrija earns 2 euros and 40 cents, which is 240 cents, so for twenty mowings, he earns 4800 cents.

For forty-one waterings, he earns 3075 cents, so his total earnings are 7875 cents.

$7875 \div 3 = 2625$ cents, which is 26 euros and 25 cents, and this is the amount Andrija will donate.