It’s one of the most common and frustrating scenarios in 11+ preparation. You review your child’s mock exam paper and see marks lost on questions you know they understand. A misplaced decimal point, a simple addition error, a misread question – these “silly mistakes” can be the difference between a pass and a fail.
But these aren’t really “silly” mistakes. They are symptoms of deeper issues, usually a combination of two things: a tendency to rush under pressure, and foundations that aren’t as solid as they seem.
The good news is that accuracy is a skill that can be taught and practised. At elevenplus.com, we believe in a two-pronged attack: first, strengthening the foundations, and second, playing “The Accuracy Game” to catch any errors that slip through.
This guide will teach you 5 simple, powerful techniques you can share with your child to dramatically reduce careless errors, boost their scores, and build their mathematical confidence.
In this guide, you will learn:
- The real root cause of most “silly mistakes.”
- 5 practical techniques to build a powerful checking habit.
- How to turn accuracy into a fun and rewarding game.
- Worked examples showing each technique in action.
The Real Cause of ‘Silly’ Mistakes
Before we get to the techniques, it’s important to understand where most errors come from. After misreading the question, the single biggest cause of mistakes on a Maths paper is a lack of instant, effortless recall of times tables.
When a child has to pause and think “what is 7 x 8?”, it uses up precious mental energy and time. This cognitive load makes them more likely to make a mistake in the next step of the calculation. True fluency in times tables is the foundation of mathematical accuracy.
The techniques below are your essential safety net to catch the errors that happen under pressure, but they work best when built upon rock-solid foundations.
The 5 Rules of the Accuracy Game
Winning this game means making these five techniques a non-negotiable part of solving every single maths problem.
1. The Estimation Check
Before your child even picks up their pencil to calculate, they should play this mini-game: “What should the answer roughly be?”
- The Technique: Look at the numbers and round them to the nearest simple value to get a quick, “ballpark” figure.
- Why it Works: This creates a mental safety net. If their final calculated answer is wildly different from their estimate, it immediately flags that something has gone wrong.
Example:
- Question: What is 49 x 19?
- Estimation Check: This is roughly 50 x 20, which is 1000. The answer should be a little less than 1000.
- Calculation: 49 x 19 = 931. This is close to the estimate. If they had calculated 9,310 or 491, the estimation check would instantly tell them to try again.
2. The “Prove It” Method (Inverse Operations)
This is the most powerful checking tool. Once your child has an answer, they must “prove it” by working backwards using the opposite (or inverse) operation.
- The Technique:
- If you added, check by subtracting.
- If you subtracted, check by adding.
- If you multiplied, check by dividing.
- If you divided, check by multiplying.
- Why it Works: It forces a completely different calculation, making it highly unlikely you’ll make the same mistake twice.
Example:
- Calculation: 345 – 167 = 178.
- “Prove It” Check: Does 178 + 167 = 345? Yes, it does. The answer is correct.
3. The “Underline The Details” Rule
Many errors come from simply misreading the question. You must train your child to slow down and become a “question detective.”
- The Technique: Before starting, underline every piece of numerical data AND the specific instruction word in the final question (e.g. “total”, “difference”, “altogether”).
- Why it Works: It forces them to engage with the details of the question and prevents them from jumping to a conclusion based on a quick scan.
Example:
- Question: “Sarah has 120 sweets. She gives a quarter to her brother and eats 15 herself. How many sweets does she have left?”
- Underlining: A child should underline “120 sweets“, “a quarter“, “eats 15“, and the crucial final question “How many sweets does she have left?“.
- The Impact: This prevents the common mistake of only calculating the first step (1/4 of 120 = 30) and stopping there. The underlining highlights that there are two deductions and a final “how many are left” calculation to perform.
[Image: A sample word problem from an elevenplus.com practice paper with key numbers and instruction words clearly underlined.]
4. The “Units Scan”
Examiners love to catch children out with mixed units. The “Units Scan” is a quick check to prevent this common trap.
- The Technique: Before calculating, quickly scan the question for different units of measurement (e.g. pence and pounds, cm and metres, minutes and hours). If you see them, convert everything to the same unit before you start.
- Why it Works: It prevents errors like adding 80p to £1.75 and getting 81.75.
Example:
- Question: A ribbon is 2.5 metres long. I cut off 60cm. How much is left in cm?
- Units Scan: I see “metres” and “cm”. I must convert. 2.5 metres = 250cm.
- Calculation: 250cm – 60cm = 190cm.
5. The “Answer Box Double-Check”
The final step before moving on. This check ensures the answer directly addresses the specific question asked.
- The Technique: Reread the underlined final question and look at your answer. Do they match? If the question asks “How much more…”, is your answer a difference? If it asks for the answer “in grams,” is your answer in grams?
- Why it Works: It catches out students who have done a correct calculation but haven’t actually answered the question that was asked.
Example:
- Question: “A school trip has 3 buses, each with 45 seats. 112 students go on the trip. How many empty seats are there in total?”
- The Common Mistake: A child might correctly calculate the total number of seats (3 x 45 = 135) and then stop, writing 135 in the answer box.
- The Double-Check: By rereading the underlined question “How many empty seats…”, the child is prompted to perform the final, crucial step: 135 – 112 = 23. The correct answer is 23.
Making it a Habit
True mathematical confidence comes from knowing your work is not just done, but done right.
Encourage your child to focus on two things: strengthening their core (especially times tables) and using these five checking techniques on every single question. By making accuracy a conscious part of the process, you can eliminate the careless errors that cost valuable marks and build the resilience needed for exam day.
Ready to put these accuracy skills to the test?
➡️ Our interactive Maths quizzes on elevenplus.com provide instant feedback, allowing your child to practice these checking methods in a fun, low-pressure environment.
