This week, I posed to you this question and this sequence of numbers:

“Assume you’re using a basic calculator and you press the numbers in the order shown, replacing each question mark with a mathematical sign. Add, subtract, multiply and divide can each be used only once. What’s the highest number you can possibly get?”

**5 ? 4 ? 7 ? 3 ? 2**

**After the break we’ll take a look at the answer, so click on through!**

**The key to working this one out is simply logic – you’re aiming for the highest number possible, so everything you do needs to make the end result bigger.**

**Let’s ignore the order of the sequence for now and look at the numbers and signs: 2, 3, 4, 5, 7 and then +, -, * and /.**

**To make the biggest number possible, we obviously need to multiply by the largest number. So, *7.**

**We need to divide by the smallest number, so /2.**

We have addition and subtraction left – we add the remaining biggest number and subtract the remaining smallest: **+4 **and **-3 **(we can’t use 5 because it’s at the start of the sequence).

Therefore, filling in the blanks, we have **5 + 4 * 7 – 3 / 2 = 30.**

So how did you do?

Vel.

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May 16, 2010 at 1:50 pm

That one was too easy, slacker 😛

May 16, 2010 at 5:02 pm

My apologies – I’ll find something devilishly hard for tomorrow 😉

May 23, 2010 at 7:01 am

Not that I don’t agree about multiplying by the largest, adding the second largest etc etc, but..

5 + (4*7) – (3/2) would be the order of calculating this, wouldn’t it? 5 + 28 – 1.5 = 31.5.

*runs back to smart-alec corner*

May 23, 2010 at 10:00 am

Hi Koch,

I see what you’re getting at with the order of operations, but if you really were using a physical calculator to do this then you would have to work everything out as you went along, rather than using brackets.

If you came across 5 + 4 * 7 – 3 / 2 written down on a page then doing it your way would be correct, but you wouldn’t actually see that if you used a calculator.

If that makes sense 😀

May 24, 2010 at 10:13 am

And here I was just about to post a lengthy reply about proper calculators accepting lines of text and all… before I actually read the orinial post:

“Assume you’re using a basic calculator”

*grumbles* I seems your kung-fu math is superiour to mine, old man.

May 24, 2010 at 11:36 pm

Every time, my young padawan 😉