Difference between revisions of "2021 JMPSC Accuracy Problems/Problem 14"
(→Solution) |
Mathdreams (talk | contribs) |
||
Line 14: | Line 14: | ||
~Bradygho | ~Bradygho | ||
+ | |||
+ | == Solution 2 == | ||
+ | |||
+ | By multiplying out <math>16 \cdot 25</math>, <math>161 \cdot 252</math>, and <math>1616 \cdot 2525</math>, we notice that the first <math>2</math> digits don't change even when we continue to add more digits. With this observation, we can conclude that the first digit of the product is <math>4</math>. | ||
+ | |||
+ | ~ Mathdreams |
Revision as of 11:38, 11 July 2021
Problem
What is the leftmost digit of the product
Solution
We notice that
In addition, we notice that
Since
We conclude that the leftmost digit must be .
~Bradygho
Solution 2
By multiplying out ,
, and
, we notice that the first
digits don't change even when we continue to add more digits. With this observation, we can conclude that the first digit of the product is
.
~ Mathdreams