What is a plus b times c equal 25 Using just 2 4 5 7 9 for a b and c?

Answer 1

This is a problem in my granddaughter's Math book. I cannot solve it. Do you have an answer and procedure to get it? It's logic, not calculus...you just have to arrange the variables in an algebraic formula to test your possibilities. a + b x c = 25...(a +b) x c = 25 won't work for any of your available numbers, because only 5 x 5 will get you 25 and there's no two numbers (using ( a + b)) in your list of "possibles" that add up to 5... so using a + (b x c) = 25 must be the formula. Your question doesn't say if you can only use a number once...but if that's the case...keep looking at the possibilities. So what number (plus) two numbers multiplied will get you 25? Note: equations are still equal if you add, subtract, multiply or divide the numbers on both sides of the equal sign (=) by the same number. 2 + (b x c) = 25 can be written 2 - [2] + (b x c) = 25 - [2]. so you eliminate the 2 on the left side of the equation [2 - 2 is 0] and on the right side subtracting [25 -2] gives you (b x c) = 23. That won't work...because no two "possible" numbers multiplied will equal 23. 4 + (b x c) = 25? Eliminate the 4 on the left by subtracting 4 from each side...4 [- 4] + (b x c) = 25 [- 4]. It becomes (b x c) = 21. no...because only 7 x 3 = 21 and you don't have a 3 in your possible numbers. (5 + (b x c) = 25?) take 5 from each side...5 [- 5] + (b x c) = 25 [- 5] gives you (b x c) = 20. No...because you don't have two 5s you can use...etc. The answer is there...keep working the equations using each "possible answer for "a". 7 + (b x c) = 25...9 + (b x c) = 25