We need to solve the following problems: Problem 4: $6237 + 6959 = ?$ Problem 5: $43.2 - 7.85 = ?$ Problem 6: $36 \times 25 = ?$

1. Problem Description

We need to solve the following problems:

Problem 4: $6237 + 6959 = ?$

Problem 5: $43.2 - 7.85 = ?$

Problem 6: $36 \times 25 = ?$

2. Solution Steps

Problem 4: Addition

$6237 + 6959$

$7 + 9 = 16$, write down 6, carry over 1

$3 + 5 = 8 + 1 = 9$

$2 + 9 = 11$, write down 1, carry over 1

$6 + 6 = 12 + 1 = 13$

So $6237 + 6959 = 13196$

Problem 5: Subtraction

$43.2 - 7.85$

Write $43.2$ as $43.20$

$43.20 - 7.85$

$0 - 5$, borrow 1 from 2, so $10 - 5 = 5$

$1 - 8$, borrow 1 from 3, so $11 - 8 = 3$

$2 - 7$, borrow 1 from 4, so $12 - 7 = 5$

$3 - 0 = 3$, so $3-0 = 3$ becomes $3$ as we borrowed from 4

Therefore, $43.2 - 7.85 = 35.35$

Problem 6: Multiplication

$36 \times 25$

$36 \times 5 = (30 \times 5) + (6 \times 5) = 150 + 30 = 180$

$36 \times 20 = (36 \times 2) \times 10 = 72 \times 10 = 720$

$36 \times 25 = 180 + 720 = 900$

3. Final Answer

Problem 4: $13196$

Problem 5: $35.35$

Problem 6: $900$