If 4 is subtracted from ones digit of two digit number and 4 is added to tens digit the resulting no. Is doubled. Find the number
let the original number be 10a + b
where a is the tens digit and b is the units digit.
New number: 10(a+4) + b-4, where 4 < b < 9
10(a+4) + b-4 = 2(10a + b)
10a + 40 +b-4 = 20a + 2b
10a + b = 36
a = (36-b)/10
the only value of b which would make 36-b a multiple of 10 is b = 6
if b=6 , then a = 3
original number is 36
check:
original tens digit -->3
original unit digit --> 6
new tens digit ---> 3+4 = 7
new unit digit --- 6-4 = 2
new number = 72
Is 72 twice 36 ?? , YES