Meet Ndalo. He is 10 years old and in Grade 5 at the village school. Ndalo always comes top of his class. "What's his secret?" his schoolmates ask themselves.

"He's excellent in reading and writing. How does he do it?" they wonder. Ndalo tells them it is because he reads lots of books. While they waste their time doing nothing, he spends all his free time reading.

Ndalo sometimes earns R80 a week in pocket money. He spends most of the pocket money on books at the second-hand book shop in his village.

So how does Ndalo earn enough pocket money for these books? Read on to find out.

Meet Pendo, the family's milking cow. She produces over 20 litres of milk per day. Ndalo's father sells the milk.

A cow needs food and water, and time to graze in the veld. So each day after school Ndalo helps with this work. Ndalo's father gives him pocket money for the work he does. And it is this money that Ndalo saves to buy books each week.

First, Ndalo gives Pendo a bunch of carrots. He gives her exactly eight carrots a day. Each day he picks the carrots from his father's vegetable patch, enough for a day at a time.

You can work it out. You will find that Pendo eats nearly 60 carrots a week. Can you tell exactly how many?

After that, Ndalo takes Pendo to graze in the fields. His father warned him to watch the time and not give Pendo more than three quarters of an hour to graze.

Pendo usually starts grazing at about quarter past two, so that Ndalo can take her back to the milking shed at 3 o'clock. In winter when it gets dark earlier, Ndalo may start grazing earlier, around half past one.

Next Ndalo gives Pendo water. Without water Pendo won't produce milk, no matter how much Ndalo feeds her. Ndalo fetches buckets of water from the village pump because there isn't one nearby.

Pendo's trough holds about 30 litres of water. Ndalo's bucket only holds 5 litres. So to fill the trough Ndalo has to make many trips. Can you work out how many trips he has to make?

Then, Ndalo takes Pendo to his father to get her daily 12 kg bag of grain. Ndalo calculates that's almost 90 kg a week.

Each bag costs R39. Ndalo works out the cost of grain for each week. First he works out the cost of 7 bags at R40, which makes R280. Then he subtracts R7 to get R273. "That's over R1 000 a month!" Ndalo estimates. Is he correct?

Ndalo's father milks Pendo twice a day. She produces about 24 litres of milk a day, so about 12 litres for each milking.

Sometimes Ndalo helps with the milking but it is not as easy as it looks. "One day," he thinks to himself, "I will have my own cows and I will have to do all the milking myself."

His father pours the milk from the big bucket into smaller two litre cans or one litre bottles. He then sells the milk for R8 a litre.

Once a week Ndalo's father donates 25 litres of milk to the school feeding scheme. Each child gets a quarter litre of this milk. That means that 100 children get milk on this day.

For each litre of milk sold, his father gives Ndalo 50c. That doesn't sound like a lot, but if his father sells 24 litres a day, it adds up to quite a bit. Can you tell how much?

Ndalo saves his money until Saturday when he makes a trip to the book shop. Each book costs less than R10, so in a good week, he can buy quite a few.

Ndalo also loves to drink Pendo's milk. His father says that milk helps to build strong bones and teeth and makes a person fit and healthy.

So by drinking milk and eating lots of vegetables from his father's garden, Ndalo is strong and healthy. He seldom gets sick and never goes hungry.

Ndalo never forgets to thank Pendo at the end of each day. He rewards her with extra carrots or spinach leaves that he finds lying around the garden.

"Thank you Pendo, you are my best friend! It is thanks to you that I am strong, healthy and clever. If not for you I would never be able to buy all the books that help me be top of my class."