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Advent calendar 2021
15 December
All 2021 advent puzzles
~
More information
The odd numbers are written in a pyramid.
(row 1)
1
(row 2)
3
5
(row 3)
7
9
11
etc.
What is the mean of the numbers in the 19th row?
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The mean of the numbers in the \(n\)th row is \(n^2\), so the mean of the number in the 19th row is
361
.
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Advent calendar 2025
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List of all puzzles
Tags
polynomials
factors
xor
clocks
calculus
geometric means
sum to infinity
lines
probability
people maths
sequences
addition
integers
sums
trigonometry
palindromes
number
median
probabilty
indices
averages
colouring
remainders
crosswords
spheres
digital clocks
pentagons
prime factors
quadratics
folding tube maps
integration
the only crossnumber
tournaments
axes
lists
coins
polygons
angles
multiplaction squares
quadrilaterals
2d shapes
ellipses
multiples
chess
routes
matrices
area
christmas
surds
combinatorics
functions
rectangles
means
planes
determinants
perfect numbers
prime numbers
cube numbers
chocolate
albgebra
complex numbers
speed
pascal's triangle
arrows
irreducible numbers
cubics
volume
products
consecutive numbers
regular shapes
hexagons
parabolas
shapes
triangle numbers
circles
partitions
medians
geometry
decahedra
factorials
star numbers
perimeter
ave
books
tiling
proportion
dates
square numbers
division
multiplication
expansions
consecutive integers
dice
squares
unit fractions
grids
digits
doubling
dodecagons
rugby
games
time
numbers
menace
logic
chalkdust crossnumber
mean
triangles
3d shapes
cryptic clues
odd numbers
percentages
gerrymandering
binary
money
coordinates
taxicab geometry
range
powers
advent
differentiation
geometric mean
graphs
bases
square roots
tangents
neighbours
wordplay
even numbers
square grids
cards
digital products
symmetry
dominos
elections
algebra
sets
crossnumbers
shape
floors
balancing
fractions
cryptic crossnumbers
sport
scales
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