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🧙‍♂️ Near‑Doubles Treasure Hunt

Master the quick‑add trick for numbers that are almost the same and solve exam‑style problems with confidence.

You step into the grand **Maths Castle ➕** and the friendly 🧙 Maths Wizard greets you with a sparkle in his eye. He tells a tale of a bustling market where a clever kid buys two packs of stickers: one pack has 7 stickers, the other has 8. Instead of counting each sticker one‑by‑one, the kid spots a secret shortcut that saves time and impresses the stall‑owner. This shortcut is exactly what we call **adding near doubles** – a trick that works whenever two numbers sit side‑by‑side on the number line, like 7 and 8 or 14 and 15. Outside school, you’ll use it when you’re sharing sweets, figuring out game scores, or helping a parent check the change after a shop visit. The wizard explains that mastering this trick means you’ll never feel stuck on a quick mental‑math challenge again, and you’ll feel proud every time you finish a problem in a flash.

So, what is a **near double**? Imagine you have a pair of numbers that are almost twins – they differ by only **one**. For example, 6 and 7, 12 and 13, or 29 and 30. When you add them, you can think of the smaller number being doubled, then simply add **one** more. It’s like saying, “Double the lower number, then add the extra one that makes the pair.” This works because 6 + 7 = (6 + 6) + 1 = 12 + 1 = 13. The idea is similar to sharing a pizza: if you know how many slices each friend gets when they both have the same amount, you just need to add the single extra slice one friend has. The wizard likens it to a magic spell: **DOUBLE‑LOWER‑PLUS‑ONE**, and once you chant it, the answer appears instantly.

Let’s see the rule in action. First, **identify the lower number** of the pair. Next, **double that lower number** – simply add it to itself. Finally, **add one** because the higher number is just one more than the lower. For instance, add 14 + 15. The lower number is 14. Doubling 14 gives 28. Adding the extra one gives 29, which is the correct total. Another example: 22 + 23. Lower is 22; double = 44; +1 = 45. Notice how we never actually add the larger number directly; we use the easier double and a tiny adjustment. This works every time the two numbers differ by one, no matter how big they are. The wizard emphasizes that the trick relies on the **difference of one**, so if the numbers differ by more than one, you need a different strategy.

Here is the step‑by‑step method you can follow whenever you see a near‑double addition: 1️⃣ **Spot the pair** – check that the numbers are exactly one apart. 2️⃣ **Pick the lower number** – the smaller of the two. 3️⃣ **Double it** – add the lower number to itself (you can use a quick mental double, e.g., 15 + 15 = 30). 4️⃣ **Add one** – because the higher number is just one more than the lower. 5️⃣ **Write the answer** – you now have the sum. Remember, the magic lies in the simplicity of “double‑lower‑plus‑one.” If you ever feel unsure, pause, repeat the steps aloud, and the answer will appear. Practising each step a few times will make the process automatic, just like a wizard’s spell that needs only a whispered incantation.

Let’s try an easy problem together: **6 + 7**. Step 1 – the numbers are one apart, so they are a near‑double pair. Step 2 – the lower number is 6. Step 3 – double 6: 6 + 6 = 12. Step 4 – add one: 12 + 1 = 13. So, 6 + 7 = 13. Notice how we never added 7 directly; we just used the double of 6 and a tiny extra. If you ever forget, think of it as “two sixes plus one extra slice.” The wizard smiles and says you’ve just unlocked the first treasure chest of the castle – the joy of fast, accurate addition!

Now for a medium‑level challenge: **23 + 24**. First, confirm they differ by one – they do, so the trick works. The lower number is 23. Double 23: 23 + 23 = 46. Add one: 46 + 1 = 47. Therefore, 23 + 24 = 47. Some pupils pause because they try to add 24 directly, which can feel slower. Remember the wizard’s tip: always start with the lower number; doubling is often quicker than adding a larger number to a smaller one. If you’re still unsure, you can also think of 24 + 23 as 24 + 20 + 3, but the near‑double method gives the answer in just two quick mental moves. You’ve now solved a problem that might appear on a timed practice test – well done!

Here’s a typical exam question you might see on a GL or CEM paper: **Question:** Using the near‑double method, what is 57 + 58? A) 115 B) 113 C) 114 D) 116 First, check the numbers: 57 and 58 differ by one, so the trick applies. Lower number = 57. Double 57: 57 + 57 = 114. Add one: 114 + 1 = 115. So the correct answer is **A) 115**. Why the other options look tempting: - B) 113 – comes from mistakenly adding 57 + 56. - C) 114 – some forget the extra one and stop at the double. - D) 116 – might result from adding 57 + 57 + 2 by mistake. The wizard points out that the key is to remember the “+1” step. By checking each option against the method, you can be confident that A is the only one that matches the calculation.

Even the best pupils slip up on near‑doubles. Here are three common errors and how to avoid them: 1️⃣ **Skipping the “+1”** – you might stop at the double (e.g., 28 + 29 → 56 instead of 57). Remember the higher number is one more, so always add that one. 2️⃣ **Doubling the wrong number** – if you double the larger number, you’ll add too much (e.g., 14 + 15 → double 15 = 30, then +1 = 31, which is wrong). Always start with the lower number. 3️⃣ **Using the trick on non‑near‑doubles** – applying it to 12 + 15 will give a wrong answer. First, check the difference; if it’s not one, use another strategy. 🧙 Maths Wizard’s #1 power tip: **“Say the rule out loud – ‘double lower, add one’ – before you calculate.** This simple chant keeps the steps clear and stops mistakes before they start. Keep practising, and the spell will become second nature!

Common mistakes

Frequently asked questions

Why do we need a special trick for these numbers?

Because the trick lets you solve the sum in just two quick steps, saving time and mental effort. You’ll finish faster and feel more confident.

What if the numbers aren’t exactly one apart?

The near‑double rule only works for pairs that differ by one. If the gap is bigger, use another strategy like normal addition or breaking the numbers apart.

I sometimes forget which number to double. Any tip?

Look at the two numbers and point to the smaller one with your finger. That’s the one you double. Practice saying ‘double lower, add one’ aloud.

Can I use this trick with very large numbers?

Yes! Whether the numbers are 7 + 8 or 127 + 128, the same steps work. The wizard’s spell is powerful for any size.

What if I make a mistake on a test?

Stay calm, reread the question, and check the three steps again. A quick review often catches the error before the exam ends.

How often will I see near‑double questions in exams?

They appear regularly in 11+ practice papers because they test speedy mental maths. Mastering them gives you a big advantage.