Question

Find the sum of all four digit numbers formef by using the digits 0, and 5, repeating any number of times in the number.​

Answer 1

My Approach:

single digit no formed = 2,4,6,8

sum= 2+4+6+8= 20

two digit= 24,26,28,42,46,48,62,64,68,82,84,86

sum= 660

three digit no=246+264+426+462+624+642=2664

268+286+628+682+826+862=3552

248+284+428+482+824+842=3108

468+486+648+684+846+864=3996

sum of all 3 digit nos =13310

Similarly for all 4 digit numbers.