Eastaway, Rob <br/><br/>
Maths on the back of an envelope :  clever ways to (roughly) calculate anything 

 - London  Harper Collins Publishers  2019 
 - vi, 200 p. 
<br/><br/><label>ISBN: </label>9780008324582 9780008324582 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Arithmetic<br/>Mathematics<br/>Popular works
<br/><br/><label>Dewey Class. No.: </label>512 EAS