The fertilizer tri-ammonium phosphate is made from 'phosphate rock' by:
1 reacting the phosphate rock with sulfuric acid. H2SO4 to produce phosphoric acid.H3 PO4
2 reacting the phosphoric acid with ammonia. NH3 , to give tri-ammonium phosphate
If the phosphate rock contains 90% by mass calcium phosphate  from which the overall yield of tri-ammonium phosphate is 95%. calculate the mass of phosphate rock required  to make 1000 tonnes of triammonium phosphate.

Hi Bhav
You can do it on a piece of paper and upload the pic here.I will check the work and in case some error is there I will correct it.

 Ca3(PO4)2 + 3H2SO4 ----> 3CaSO4 +2 H3PO4
  H3PO4 + 3NH3 ---->( NH4 )3PO4

1000 tonnes is  10^9 g of triammoniumphosphate   
Moles of triammoniumphosphate = 10^9 g *1mol (NH4)3PO4 / 149.09 g
                                                            = 6.7*10^6 moles
95 % of actual moles required = 6.7*10^6 moles

Actual moles required = 6.7*10^6 moles * 100 /95 = 7.06*10^6 moles
Moles of H3PO4 required = Moles of triammoniumphosphate=7.06*10^6 moles
Moles of Ca3(PO4)2 required = ½ Moles of H3PO4 = 3.53*10^6moles
This is 90% of actual required
Hence Rock required = 3.53*10^6moles *100 /90 = 3.92 * 10^6 moles
Grams of the rock = 3.92 * 10^6 moles*310.18 g /1mole 
                  = 1.22*10^9 g = 1220 tonnes   
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Phosphate rock is a substance that is high in phosphate minerals.Phosphate rock minerals are the only significant global resources of phosphorus.

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Degreaser

We need to make 1000 tonnes of triammonium phosphate but the yield is 95% so we need to do calculations for a little more 1053 tonnes of triammonium phosphate
Writing down the equation to find the amount of phosphoric acid;
H3PO4+3NH3---->(NH4)3PO4
m((NH4)3PO4)=1050 tonnes-----> 1053 x 10^3kg---->1053 x 10^6 g
M((NH4)3PO4)=149.12 g mol^-1
n=7061 x 10^3 mol
Since it's a 1:1 ratio
n(H3PO4)=7061 x 10^3 mol
Writing down the second equation
Ca3(PO4)2+3H2SO4---->2H3PO4+ 3CaSO4
Since it's a 1:2 ratio
n(Ca3(PO4)2)=3531 x 10^3 mol
M(Ca3(PO4)2=310.18 g mol^-1
m(Ca3(PO4)2)=1095 x 10^6 g
Since the phosphate rock itself contains 90% by mass of the Ca3(PO4)2, then the mass of the phosphate rock we need is:
1095 x 10^6/ 0.90= 1217 x 10^6 g-----> 1217 tonnes
The answer is 1217 tonnes of phosphate rock is needed in order to get 1000 tonnes of tri-ammonium phosphate.