Question

In a school , students decided to plant trees is and around the school to reduce air pollution. It was decided that number of trees, that each section of each class will plant will be double of the class in which in which they are studying . If there are 1 to 12 classes in the school and each class has two section find how many trees were planted by the student

Answer 1

1×2+2×2+3×2+4×2+5×2+6×2+7×2+8×2+9×2+10×2+11×2+12×2=156×2=312

Answer 2

1x2+1x2+2x2+2x2+3x2+3x2+4x2+4x2+5x2+5x2+6x2+6x2+7x2+7x2+8x2+8x2+9x2+9x2+10x2+10x2+11x2+11x2+12x2+12x2
==2+2=4+4+6+6+8+8+10+10+12+12+14+14+16+16+18+18+20+20+22+22+24+24
==4+8+12+16+20+24+28+32+36+40+44+48
===12+28+44+60+76+92
==40+104+168
==144+168
==312