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Questions Related to vedic methods of multiplication

Multiple choice multiplication and division vedic methods of multiplication vedic mathematics history of mathematics maths

The sum of all two digit numbers divisible by $5$ is:

  1. $1035$
  2. $1245$
  3. $1230$
  4. $945$
  5. None of these

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Required numbers are $10,15,20,25,......96$
This is an A.P. in which $a=10,d=5$ and $l=95$
${t} _{n}=95$ $\Rightarrow$ $a+(n-1)d=95$
$\Rightarrow$ $10+(n-1)\times 5=95$
$\Rightarrow$ $(n-1)\times 5=85$
$\Rightarrow$ $(n-1)=17$
$\Rightarrow$ $n=18$
$\therefore$ Required Sum $=\cfrac { n }{ 2 } (a+l)=\cfrac { 18 }{ 2 } \times (10+95)=(95\times 105)=945$