Two 2s can be combined in many ways to express different numbers. Here are some!

2-2=0

2/2 = 1

2 + 2 = 2.2

(2^2)! = 24 (4! means 4x3x2x1) (2^2 is 2 to the power of 2)

Can you write an expression that has the value of exactly 5, using:

- Two, and only two, 2s, and
- Any mathematical symbols or operations?

**Answer**: This teaser was a test of both maths and keyboard skills:

**Andrew Knox**, Rubbond International, Ohé en Laak, The Netherlands;

The square root of (.2 to the power of minus 2), i.e. the square root of (1/.2) x (1/.2), or the square root of 1 divided by .04, or the square root of 25.

**John Bowen**, consultant, Bromsgrove, UK:

Sq Rt of [0.2 to the power of -2] =5 / ie Sq Rt [1/0.04]

**Michele ****Girard**i, Scame Mastaf Spa, Suisio, Italy;

5= sqroot(25)=sqroot(100/4)

5 = Sqroot( inverse.log(2) / inverse.sqroot(2)

**Paul Knutson**, textile engineer, Timken Belts, Springfield, Missouri, USA

.2^(-2^0)

**Stephan Paischer**, head of product management special products, Semperit AG Holding, Vienna, Austria;

**Chrystelle Tandonnet** and I**ndrayush**** De**, application & technology development, KSB SAS Pompes. Gradignan, France:

SQR(.2^-2)

√ (0.2^-2)

And finally this extra one given by a “mathematician passing nearby” Michele Girardi’s desk: 5 = (2-i)*(2+i).

Well done to all above and everyone else who had a go.