Sunday Afternoon Maths XVIII

 Posted on 2014-06-22 

Seven digits

"I'm thinking of a number. I've squared it. I've squared the square. And I've multiplied the second square by the original number. So I now have a number of seven digits whose final digit is a 7," said Dr. Dingo to his daughter.
Can you work out Dr. Dingo's number?

Show answer & extension

Tags: numbers


On a graph of \(y=x^2\), two lines are drawn at \(x=a\) and \(x=-b\) (for \(a,b>0\). The points where these lines intersect the parabola are connected.
What is the y-coordinate of the point where this line intersects the y-axis?

Show answer & extension

If you enjoyed these puzzles, check out Sunday Afternoon Maths LXVII,
puzzles about menace, or a random puzzle.


Show me a random puzzle
 Most recent collections 

Sunday Afternoon Maths LXVII

Coloured weights
Not Roman numerals

Advent calendar 2018

Sunday Afternoon Maths LXVI

Cryptic crossnumber #2

Sunday Afternoon Maths LXV

Cryptic crossnumber #1
Breaking Chocolate
Square and cube endings

List of all puzzles


triangle numbers pascal's triangle indices planes speed square numbers perfect numbers christmas square roots remainders perimeter money triangles squares algebra shape hexagons games circles averages chess quadratics angles routes volume percentages complex numbers odd numbers addition taxicab geometry probability arrows dodecagons ave probabilty calculus colouring advent shapes multiplication coins logic crosswords division bases rugby symmetry scales factorials ellipses differentiation parabolas factors sequences folding tube maps crossnumbers sums surds functions graphs chocolate proportion sum to infinity menace 2d shapes area geometry fractions integers palindromes mean star numbers cube numbers polygons chalkdust crossnumber clocks cryptic crossnumbers balancing sport time grids number multiples dates floors spheres regular shapes rectangles means cryptic clues cards unit fractions digits people maths partitions wordplay integration dice trigonometry numbers coordinates lines irreducible numbers doubling 3d shapes books prime numbers


Show me a random puzzle
▼ show ▼
© Matthew Scroggs 2019