Some US scientists have shown that monkeys can be quite clever with money. In one study, the monkeys are given silver ‘coins’, and are taught to use them as money. They get the idea very fast. The monkeys can ‘buy’ pieces of apple or pieces of banana. When a piece of apple costs the same as a piece of banana, the monkeys buy each fruit the same number of times. But when the apple pieces go ‘on sale’, the monkeys lose interest in banana. They choose apple, because they get more fruit for the same money.

When pieces of cucumber were offered as well, one group of monkeys did something interesting. They didn’t eat the cucumber pieces. They saw that the cucumber pieces were the same size as their silver coins. They hid the silver coins and tried to use the cucumber pieces as money.

The scientists are very interested, but they are also getting a bit worried. They have discovered that the monkeys can become enthusiastic gamblers, too!
(TARGET, Longman)

I have four questions to the passage.
1. Paragraph one uses the present simple tense, while paragraph two uses the past simple tense. Why?
2. Teachers always tell us to say ‘I like apples.’ not ‘I like apple’. But why does the writer say ‘pieces of apple’ (not apples) and ‘…the monkeys lose interest in banana (not bananas). They choose apple (not apples)…’?
3. But when the apple pieces go ‘on sale’, the monkeys lose interest in banana. Here “go ‘on sale’” is American English. What’s the British English for that?
4. …the monkeys buy each fruit the same number of times. Can I just say ‘the same times’ instead of ‘the same number of times’?

Originally Posted by diamondcutter

Some US scientists have shown that monkeys can be quite clever with money. In one study, the monkeys are given silver ‘coins’, and are taught to use them as money. They get the idea very fast. The monkeys can ‘buy’ pieces of apple or pieces of banana. When a piece of apple costs the same as a piece of banana, the monkeys buy each fruit the same number of times. But when the apple pieces go ‘on sale’, the monkeys lose interest in banana. They choose apple, because they get more fruit for the same money.

When pieces of cucumber were offered as well, one group of monkeys did something interesting. They didn’t eat the cucumber pieces. They saw that the cucumber pieces were the same size as their silver coins. They hid the silver coins and tried to use the cucumber pieces as money.

The scientists are very interested, but they are also getting a bit worried. They have discovered that the monkeys can become enthusiastic gamblers, too!
(TARGET, Longman)

I have four questions to the passage.
1. Paragraph one uses the present simple tense, while paragraph two uses the past simple tense. Why? In the first paragraph, it's describing the procedure. Compare it to this:

The gambler put down three cards and asked the dealer to give him three more. In the game of draw poker, you can trade up to three cards to improve your hand. But the three new cards were no better than the ones he had traded them for.

As you can see, your writer was doing something similar.

2. Teachers always tell us to say ‘I like apples.’ not ‘I like apple’. But why does the writer say ‘pieces of apple’ (not apples) and ‘…the monkeys lose interest in banana (not bananas). They choose apple (not apples)…’? Teachers often generalize. In this case, "apple" and "apples" mean the same thing and are both correct.

3. But when the apple pieces go ‘on sale’, the monkeys lose interest in banana. Here “go ‘on sale’” is American English. What’s the British English for that? I don't know. I'm an American.

4. …the monkeys buy each fruit the same number of times. Can I just say ‘the same times’ instead of ‘the same number of times’? No. It would be meaningless. You could say "at the same time," but that would mean simultaneously, in unison, all at once.