Friday

February 27, 2015

February 27, 2015

Posted by **Anonymous** on Tuesday, March 26, 2013 at 11:20pm.

- Algebra -
**Ian**, Friday, March 29, 2013 at 8:20pmab = 75

Archaic solution: only possibilities for ab are 01 through 99. Eliminate all of those not divisible by 5, which leaves: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55. 60, 65, 70, 75, 80, 85, 90, and 95. Eliminate those not divisible by 3 (divisibility rule for 3) , which leaves 15, 30, 45, 60, 75, and 90. Now eliminate those not divisible by 7, which leaves ab = 75. Divisibility rule for 7: double the last digit and subtract from the remaining digits. If the ramaining digits are divisible by 7, then the original number is divisible by 7. So, our number is 12075. 5 + 5 =10. Subtracting: 1207 - 10 = 1197. 1197mod7 has no remainder, thus our solution.

**Answer this Question**

**Related Questions**

math, geometry - The bases of trapezoid ABCD are \overline{AB} and \overline{CD...

MATH_URGENT - The bases of trapezoid ABCD are \overline{AB} and \overline{CD}. ...

math - The bases of trapezoid ABCD are \overline{AB} and \overline{CD}. Let P be...

math - Let ABCD be a cyclic quadrilateral. Let P be the intersection of \...

Geometry - Points D, E, and F are the midpoints of sides \overline{BC}, \...

geometry - Points D, E, and F are the midpoints of sides \overline{BC}, \...

geometry - Points D, E, and F are the midpoints of sides \overline{BC}, \...

MATH_URGENT - Let M be the midpoint of side \overline{AB} of \triangle ABC. ...

Maths - a and b are digits such that 120abŻŻŻŻŻŻŻŻ is a multiple of 3, 5 and 7. ...

precalculus - The equation of the line joining the complex numbers -5 + 4i and 7...