Let the number be 2ab,a+b=13 ⇒a,b∈{0,9} ⇒6 numbers {(9,4),(8,5)...(4,9)} Similarly, for 3ab,a+b=12⇒7 numbers For 4ab,a+b=11⇒ Numbers For 5ab, a+b=10⇒9 numbers For 6ab, a+b=9⇒10 numbers For 7ab,a+b=8⇒9 numbers For 8ab, a+b=7⇒8 numbers For 9ab, a+b=6⇒7 numbers ∴‌‌ Total ways =64.