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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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Most recent collections
Advent calendar 2024
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List of all puzzles
Tags
irreducible numbers
angles
coins
geometric mean
geometry
time
cryptic clues
symmetry
folding tube maps
unit fractions
functions
rugby
complex numbers
partitions
sport
colouring
consecutive integers
hexagons
shape
balancing
expansions
factorials
surds
logic
binary
factors
even numbers
sums
coordinates
graphs
probability
decahedra
taxicab geometry
percentages
proportion
people maths
quadrilaterals
square numbers
multiples
quadratics
trigonometry
squares
lines
ave
matrices
numbers
dodecagons
combinatorics
determinants
square roots
perfect numbers
rectangles
dice
division
calculus
products
doubling
albgebra
median
digital products
crossnumbers
integers
averages
planes
multiplication
games
routes
shapes
regular shapes
neighbours
parabolas
cube numbers
cryptic crossnumbers
area
number
gerrymandering
addition
polynomials
ellipses
axes
pentagons
speed
advent
triangle numbers
powers
2d shapes
chalkdust crossnumber
wordplay
sets
chess
christmas
tournaments
numbers grids
books
chocolate
dates
integration
differentiation
clocks
mean
volume
scales
crossnumber
3d shapes
polygons
sequences
crosswords
odd numbers
star numbers
elections
tangents
remainders
digital clocks
cubics
means
geometric means
menace
fractions
medians
algebra
pascal's triangle
perimeter
floors
probabilty
sum to infinity
consecutive numbers
grids
bases
the only crossnumber
digits
cards
money
range
spheres
triangles
dominos
square grids
arrows
palindromes
prime numbers
indices
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tiling
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