# Post: Reactive discussion + peer exercise¶

## 2019¶

Have a general chat with students:

• How did they find things?

Start by highlighting that we have seen 3 things:

• Variable assignment (3 types: numeric, string and boolean);
• If statements;
• While loops.

Explain that today we will go over exercise 4 and 5.

Before doing that: show that this is going to be a very small modification of tutorial 4.

After discussing the code run with nbtutor, include %load_ext nbtutor in a cell and then include %%nbtutor in a given cell.

Highlight the role of indentation and the difference between both examples.

Now as a class, aim to find the number of the numbers less than 500 that are perfect squares:

$|\{n \in \mathbb{N} | \sqrt{n} \in \mathbb{Z} \text{ and }n \leq 500\}|$

Before we start show:

>>> import math
>>> n = 64
>>> int(math.sqrt(n)) ** 2 == n
True
>>> int(math.sqrt(n + 1)) ** 2 == n + 1
False


In groups write down some code to do this.

Show a solution:

>>> upper_limit = 500
>>> number = 0
>>> count = 0
>>> while number < upper_limit:
...     number += 1
...     if int(math.sqrt(number)) ** 2 == number:
...         count += 1
>>> count
22


Discuss possible modifications, for example how to print them, but also what about finding the 500th perfect square?:

>>> upper_limit = 500
>>> number = 0
>>> count = 0
>>> while count < upper_limit:
...     number += 1
...     if int(math.sqrt(number)) ** 2 == number:
...         count += 1
>>> number
250000


If there is time, explain that question 6 is difficult. Ask them to use it by hand to find the sqrt of a 4 and 5. Immediately should arrive at the problem of how to start?