New Post: converting Text to Numeric form

I have made this sheet using PHPExcel
i filled it using an array .

it has values in percent form and it treated as text form by default .
how can i convert my all the columns in to numeric form for so i can apply some math formulas on it .

   $excel_out_Questions = $this->outputQuestions($Sets);

   $objPHPExcel->getActiveSheet()->fromArray($excel_out_Questions, "" , 'A5');

i have tried this but it doesn't work ... :/

  $objPHPExcel->getActiveSheet()->getStyle('B434:B444')->getNumberFormat()->setFormatCode (PHPExcel_Style_NumberFormat::FORMAT_NUMBER_00);

$objPHPExcel->getActiveSheet()->setCellValue( 'B445','=(SUM(B443:B444)-SUM(B434:B440))*100)');

Please suggest.

Thanks in advance