mathematics
By gagan_nk
@gagan_nk (4)
India
October 20, 2006 3:09am CST
A two digit number is four times the sum of its digits and twice the product of the digits. Find the number
7 responses
@RAMPersona (2033)
• Philippines
23 Oct 06
Solution:
let x be the 2 digit no
i = 1st digit
j = 2nd digit
given:
x = 4(i+j)
** x = 10i+j (base 10 or decimal)
by substitution:
4(i+j) = 10i+j
4i+4j = 10i+j
4j-j = 10i-4i
3j = 6i
j = 2i
also given,
x = 2ij
by substitution:
4(i+j) = 2ij
4(i+2i) = 2i(2i)
4(i+2i) = 4i²
i+2i = i²
3i = i²
* i = 3
and,
j = 2i
j = 2(3)
* j = 6
so,
x = 10i+j
x = 10(3)+6
* x = 36 *
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